GL: Clamp uniform array access on Android and AMD devices.

include/platform/FeaturesGL.h

@@ -292,6 +292,12 @@ struct FeaturesGL : FeatureSetBase
         "Using glClear for robust resource initialization is buggy on some drivers and leads to "
         "texture corruption. Default to data uploads except on MacOS where it is very slow.",
         &members, "http://crbug.com/883276"};
+
+    // Some drivers automatically handle out-of-bounds uniform array access but others need manual
+    // clamping to satisfy the WebGL requirements.
+    Feature clampArrayAccess = {"clamp_array_access", FeatureCategory::OpenGLWorkarounds,
+                                "Clamp uniform array access to avoid reading invalid memory.",
+                                &members, "http://anglebug.com/2978"};
 };
 
 inline FeaturesGL::FeaturesGL()  = default;

src/libANGLE/renderer/gl/ShaderGL.cpp

@@ -328,6 +328,11 @@ std::shared_ptr<WaitableCompileEvent> ShaderGL::compile(const gl::Context *conte
         additionalOptions |= SH_SELECT_VIEW_IN_NV_GLSL_VERTEX_SHADER;
     }
 
+    if (features.clampArrayAccess.enabled)
+    {
+        additionalOptions |= SH_CLAMP_INDIRECT_ARRAY_BOUNDS;
+    }
+
     options |= additionalOptions;
 
     auto workerThreadPool = context->getWorkerThreadPool();

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -1507,6 +1507,10 @@ void InitializeFeatures(const FunctionsGL *functions, angle::FeaturesGL *feature
     features->limitMaxMSAASamplesTo4.enabled    = IsAndroid();
 
     features->allowClearForRobustResourceInit.enabled = IsApple();
+
+    // The WebGL conformance/uniforms/out-of-bounds-uniform-array-access test has been seen to fail
+    // on AMD and Android devices.
+    features->clampArrayAccess.enabled = IsAndroid() || IsAMD(vendor);
 }
 
 void InitializeFrontendFeatures(const FunctionsGL *functions, angle::FrontendFeatures *features)