Add ANGLE Platform implementation.

ui/gl/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
 
@@ skipping 165 matching lines @@
     configs += [
       "//build/config/linux:x11",
       "//build/config/linux:xcomposite",
       "//build/config/linux:xext",
     ]
 
     deps += [ "//ui/gfx/x" ]
   }
   if (is_win) {
     sources += [
+      "angle_platform_impl.cc",
+      "angle_platform_impl.h",
       "gl_bindings_autogen_wgl.cc",
       "gl_bindings_autogen_wgl.h",
       "gl_context_wgl.cc",
       "gl_context_wgl.h",
       "gl_egl_api_implementation.cc",
       "gl_egl_api_implementation.h",
       "gl_surface_wgl.cc",
       "gl_surface_wgl.h",
       "gl_wgl_api_implementation.cc",
       "gl_wgl_api_implementation.h",
@@ skipping 83 matching lines @@
     deps = [
       ":surface_jni_headers",
     ]
     sources = [
       "../android/java/src/org/chromium/ui/gl/SurfaceTextureListener.java",
       "../android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java",
     ]
     jni_package = "ui/gl"
   }
 }