When ANGLE is enabled for an app, show a dialog box to the user to
indicate that ANGLE is in use.   This is useful because there are
not (or at least shouldn't be) any visual indication that a different
OpenGL driver is in use.

Clean up some missed renaming/logging related to the "Enable ANGLE for
all" setting.

Bug: angleproject:3006
Test: Load an app with ANGLE enabled and verify dialog box is shown.
Test: Load an app without ANGLE and verify dialog box is not shown.
Change-Id: I46ec89567c93efaf156a4801948cd48aabd5f4fb
Reviewed-on: https://chromium-review.googlesource.com/c/1383374Reviewed-by: Tobin Ehlis <tobine@google.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Commit-Queue: Tim Van Patten <timvp@google.com>