Update standalone Android docs.

doc/DevSetupAndroid.md

 # ANGLE for Android
 
-Building ANGLE for Android is heavily dependent on the Chromium toolchain. It is not currently possible to build ANGLE for Android without a Chromium checkout. See http://anglebug.com/2344 for more details on why.
+**Important note**: Android builds currently require Linux.
 
-From a Linux platform (the only platform that Chromium for Android supports), follow the steps in
-[Checking out and building Chromium for Android](https://chromium.googlesource.com/chromium/src/+/master/docs/android_build_instructions.md).
+## Setting up the ANGLE build for Android
 
-Name your output directories `out/Debug` and `out/Release`, because Chromium GPU tests look for browser binaries in these folders. Replacing '[Debug|Release]' with other names seems to be OK when working with multiple build configurations.
+Please follow the instructions in [DevSetup][DevSetup.md] to check out and bootstrap ANGLE with
+gclient. Then edit your `.gclient` to add `target_os = ['android']` to check out Android
+dependencies. Then run `gclient sync` to download all required sources and packages.
 
-
-## ANGLE GN args for Android
-The following command will open a text editor to populate GN args for a Debug build:
+The following command will open a text editor to populate GN args for an Android Release build:
 ```
-gn args out/Debug
+gn args out/Android
 ```
 
 Once the editor is up, paste the following GN args to generate an Android build, and save the file.
 ```
 target_os = "android"
 target_cpu = "arm64"
-android32_ndk_api_level = 26
-android64_ndk_api_level = 26
-angle_libs_suffix = "_angle"
 is_component_build = false
+is_debug = false
+dcheck_always_on = true   # Recommended for debugging. Turn off for performance.
+use_goma = true           # Googlers-only! If you're not a Googler remove this.
 ```
 
 More targeted GN arg combinations can be found [below](#android-gn-args-combinations).
 
-If you run into any problems with the above, you may be able to pull newer GN args from an official Android bot on [GPU.FYI waterfall](https://ci.chromium.org/p/chromium/g/chromium.gpu.fyi/console).
- - Look for `generate_build_files` step output of that bot.
- - Remove `goma_dir` flag.
+If you run into any problems with the above, you can copy the canonical args from CI:
+ - Visit the ANGLE [CI Waterfall](https://ci.chromium.org/p/angle/g/ci/console).
+ - Open any recent Android build.
+ - Expand the for "lookup GN args" step and copy the GN args.
+ - Always omit the `goma_dir` flag.
+ - If you are not a Googler, also omit the `use_goma` flag.
 
 ## Building ANGLE for Android
-Build an ANGLE target using the following command:
+
+Build all ANGLE targets using the following command:
 
 ```
-autoninja -C out/Debug <target>
+autoninja -C out/Android
 ```
 
-The following ANGLE build targets are supported:
+Most ANGLE build targets are supported. We do not support the ANGLE samples on
+Android currently. ANGLE tests will be in your `out/Android` directory, and can
+be run with various options. For instance, angle perftests can be run with:
 
 ```
-angle
-angle_apks
-angle_deqp_gles2_tests
-angle_deqp_khr_gles2_tests
-angle_deqp_gles3_tests
-angle_deqp_khr_gles3_tests
-angle_deqp_gles31_tests
-angle_deqp_khr_gles31_tests
-angle_deqp_egl_tests
-angle_end2end_tests
-angle_perftests
-angle_unittests
-angle_white_box_perftests
-angle_white_box_tests
-```
-ANGLE tests will be in your out/<target> directory, and can be run with various options. For instance, angle perftests can be run with:
-```
-./out/Debug/angle_perftests --use-angle=vulkan --verbose --local-output --gtest_filter="*foo*"
+./out/Android/angle_perftests --verbose --local-output --gtest_filter=DrawCallPerf*
 ```
 
-Additional details are in [Android Test Instructions](https://chromium.googlesource.com/chromium/src/+/master/docs/testing/android_test_instructions.md).
+Additional details are in [Android Test Instructions][AndroidTest].
 
 Additional Android dEQP notes can be found in [Running dEQP on Android](dEQP.md#Running-dEQP-on-Android).
 
-If you are targeting WebGL and want to run GPU telemetry tests, build `chrome_public_apk` target. Then follow [GPU Testing](http://www.chromium.org/developers/testing/gpu-testing#TOC-Running-the-GPU-Tests-Locally) doc, using `--browser=android-chromium` argument. Make sure to set your `CHROMIUM_OUT_DIR` environment variable, so that your browser is found, otherwise the stock one will run. Also, follow [How to build ANGLE in Chromium for dev](BuildingAngleForChromiumDevelopment.md) to work with Top of Tree ANGLE in Chromium.
+If you are targeting WebGL and want to run with ANGLE, you will need to build within a full
+Chromium checkout. Please follow the [Chromium build instructions for Android][ChromeAndroid].
+Also refer to the [ANGLE Guide][ANGLEChrome] on how to work with Top of Tree ANGLE in Chromium.
+Build the `chrome_public_apk` target, and follow the [GPU Testing][GPU Testing] doc, using
+`--browser=android-chromium`. Make sure to set your `CHROMIUM_OUT_DIR` environment variable, so
+that your browser is found, otherwise the tests will use the stock browser.
+
+[AndroidTest]: https://chromium.googlesource.com/chromium/src/+/master/docs/testing/android_test_instructions.md
+[GPU Testing]: http://www.chromium.org/developers/testing/gpu-testing#TOC-Running-the-GPU-Tests-Locally
+[ChromeAndroid]: https://chromium.googlesource.com/chromium/src/+/master/docs/android_build_instructions.md
+[ANGLEChrome]: BuildingAngleForChromiumDevelopment.md
 
 ## Using ANGLE as the Android OpenGL ES driver
 
-Starting with Android 10 (Q), ANGLE can be loaded as the OpenGL ES driver.
+Starting with Android 10 (Q), you can load ANGLE as your device's OpenGL ES driver.
 
-`== Important Note ==` ANGLE built this way can only be used for *DEBUGGABLE APPS* (i.e. [marked debuggable](https://developer.android.com/guide/topics/manifest/application-element#debug) in the manifest) or users with *ROOT ACCESS* (i.e. a [userdebug](https://source.android.com/setup/build/building) build).
+`== Important Note ==` You can only run this ANGLE with *DEBUGGABLE APPS* or when you have
+*ROOT ACCESS*. Debuggable apps are [marked debuggable][Debuggable] in the manifest. For root
+access, see the [Android documentation][UserDebug] for how to build from source.
 
-To build the ANGLE APK, you must first bootstrap your build by following the steps [above](#ANGLE-for-Android). The steps below will result in an APK that contains the ANGLE libraries and can be installed on any Android 10+ build.
+To build the ANGLE APK, you must first bootstrap your build by following the steps
+[above](#ANGLE-for-Android). The steps below will result in an APK that contains the ANGLE
+libraries and can be installed on any Android 10+ build.
 
-Apps can be opted in to ANGLE [one at a time](#ANGLE-for-a-single-OpenGL-ES-app), in [groups](#ANGLE-for-multiple-OpenGL-ES-apps), or [globally](#ANGLE-for-all-OpenGL-ES-apps), but they must be launched by the Java runtime since the libraries are discovered within an installed package. This means ANGLE cannot be used by native executables or SurfaceFlinger at this time.
+Apps can be opted in to ANGLE [one at a time](#ANGLE-for-a-single-OpenGL-ES-app), in
+[groups](#ANGLE-for-multiple-OpenGL-ES-apps), or [globally](#ANGLE-for-all-OpenGL-ES-apps). The
+apps must be launched by the Java runtime since the libraries are discovered within an installed
+package. This means ANGLE cannot be used by native executables or SurfaceFlinger at this time.
 
-## Build the ANGLE APK
+## Building the ANGLE APK
 
-Using 'gn args` from above, you can build the ANGLE apk using:
+Using `gn args` from above, you can build the ANGLE apk using:
 ```
-autoninja -C out/Debug angle_apks
+autoninja -C out/Android angle_apks
 ```
-## Install the ANGLE APK
+
+## Installing the ANGLE APK
+
 ```
-adb install -r -d --force-queryable out/Debug/apks/AngleLibraries.apk
+adb install -r -d --force-queryable out/Android/apks/AngleLibraries.apk
 ```
 You can verify installation by looking for the package name:
 ```
 $ adb shell pm path org.chromium.angle
 package:/data/app/org.chromium.angle-HpkUceNFjoLYKPbIVxFWLQ==/base.apk
 ```
+
 ## Selecting ANGLE as the OpenGL ES driver
 
-For debuggable applications or root users, you can tell the platform to load ANGLE libraries from the installed package.
+For debuggable applications or root users, you can tell the platform to load ANGLE libraries from
+the installed package.
 ```
 adb shell settings put global angle_debug_package org.chromium.angle
 ```
 Remember that ANGLE can only be used by applications launched by the Java runtime.
 
 ## ANGLE driver choices
+
 There are multiple values you can use for selecting which OpenGL ES driver is loaded by the platform.
 
 The following values are supported for `angle_gl_driver_selection_values`:
@@ -110,17 +120,24 @@ The following values are supported for `angle_gl_driver_selection_values`:
 In each section below, replace `<driver>` with one of the values above.
 
 ## ANGLE for a *single* OpenGL ES app
+
 ```
 adb shell settings put global angle_gl_driver_selection_pkgs <package name>
 adb shell settings put global angle_gl_driver_selection_values <driver>
 ```
+
 ## ANGLE for *multiple* OpenGL ES apps
-Similar to selecting a single app, you can select multiple applications by listing their package names and driver choice in comma separated lists.  Note the lists must be the same length, one driver choice per package name.
+
+Similar to selecting a single app, you can select multiple applications by listing their package
+names and driver choice in comma separated lists.  Note the lists must be the same length, one
+driver choice per package name.
 ```
 adb shell settings put global angle_gl_driver_selection_pkgs <package name 1>,<package name 2>,<package name 3>,...
 adb shell settings put global angle_gl_driver_selection_values <driver 1>,<driver 2>,<driver 3>,...
 ```
+
 ## ANGLE for *all* OpenGL ES apps
+
 `Note: This method only works on a device with root access.`
 
 Enable:
@@ -131,7 +148,9 @@ Disable:
 ```
 adb shell settings put global angle_gl_driver_all_angle 0
 ```
+
 ## Check for success
+
 Check to see that ANGLE was loaded by your application:
 ```
 $ adb logcat -d | grep ANGLE
@@ -139,7 +158,9 @@ V GraphicsEnvironment: ANGLE developer option for <package name>: angle
 I GraphicsEnvironment: ANGLE package enabled: org.chromium.angle
 I ANGLE   : Version (2.1.0.f87fac56d22f), Renderer (Vulkan 1.1.87(Adreno (TM) 615 (0x06010501)))
 ```
+
 ## Clean up
+
 Settings persist across reboots, so it is a good idea to delete them when finished.
 ```
 adb shell settings delete global angle_debug_package
@@ -147,7 +168,9 @@ adb shell settings delete global angle_gl_driver_all_angle
 adb shell settings delete global angle_gl_driver_selection_pkgs
 adb shell settings delete global angle_gl_driver_selection_values
 ```
+
 ## Troubleshooting
+
 If your application is not debuggable or you are not root, you may see an error like this in the log:
 ```
 $ adb logcat -d | grep ANGLE
@@ -155,41 +178,41 @@ V GraphicsEnvironment: ANGLE developer option for <package name>: angle
 E GraphicsEnvironment: Invalid number of ANGLE packages. Required: 1, Found: 0
 E GraphicsEnvironment: Failed to find ANGLE package.
 ```
-Double check that you are root, or that your application is [marked debuggable](https://developer.android.com/guide/topics/manifest/application-element#debug).
+Double check that you are root, or that your application is [marked debuggable][Debuggable].
 
 ## Android GN args combinations
 
-The [above](#angle-gn-args-for-android) GN args only modify default values to generate a Debug build for Android. Below are some common configurations used for different scenarios.
+The [above](#angle-gn-args-for-android) GN args only modify default values to generate a Debug
+build for Android. Below are some common configurations used for different scenarios.
 
-To determine what is different from default, you can point the following command at your target directory. It will show the list of gn args in use, where they came from, their current value, and their default values.
+To determine what is different from default, you can point the following command at your target
+directory. It will show the list of gn args in use, where they came from, their current value,
+and their default values.
 ```
 gn args --list <dir>
 ```
+
 ### Performance config
+
 This config is designed to get maximum performance by disabling debug configs and validation layers.
 Note: The oddly named `is_official_build` is a more aggressive optimization level than `Release`. Its names is historical.
 ```
 target_os = "android"
 target_cpu = "arm64"
-android32_ndk_api_level = 26
-android64_ndk_api_level = 26
-angle_libs_suffix = "_angle"
 is_component_build = false
 is_official_build = true
 is_debug = false
 ```
-### Release with asserts config
-This config is useful for quickly ensuring Vulkan is running cleanly. It disables debug, but enables asserts and allows validation errors.
+
+### Debug config
+
+This config is useful for quickly ensuring Vulkan is running cleanly. It disables debug, but
+enables asserts and allows validation errors.
 ```
 target_os = "android"
 target_cpu = "arm64"
-android32_ndk_api_level = 26
-android64_ndk_api_level = 26
-angle_libs_suffix = "_angle"
 is_component_build = false
-is_official_build = true
-is_debug = false
-dcheck_always_on = true
+is_debug = true
 ```
 
 #### Application Compatibility
@@ -202,7 +225,9 @@ angle_expose_non_conformant_extensions_and_versions = true
 ```
 
 ## Command line for launching chrome on Android
-[This Makefile](https://github.com/phuang/test/blob/master/chromium/Makefile) contains many useful command lines for launching chrome.
+
+[This Makefile](https://github.com/phuang/test/blob/master/chromium/Makefile) contains many useful
+command lines for launching chrome.
 
 Targets run_chrome_public_apk_* is for launching chrome on Android.
 
@@ -227,3 +252,5 @@ $ make android_symbol
 $ make gpu_unittests GTEST_FILTER="gtest-filters" # If GTEST_FILTER is not specified, all tests will be run.
 ```
 
+[Debuggable]: https://developer.android.com/guide/topics/manifest/application-element#debug
+[UserDebug]: https://source.android.com/setup/build/building