Add EXT_color_buffer_half_float extension support in GPU commandbuffer service.

ui/gl/gl_gl_api_implementation.cc

 // Copyright (c) 2012 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.
 
 #include "ui/gl/gl_gl_api_implementation.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 107 matching lines @@
 }
 
 static void GL_BINDING_CALL CustomTexStorage2DEXT(
     GLenum target, GLsizei levels, GLenum internalformat, GLsizei width,
     GLsizei height) {
   GLenum gl_internal_format = GetTexInternalFormat(internalformat);
   return g_driver_gl.orig_fn.glTexStorage2DEXTFn(
       target, levels, gl_internal_format, width, height);
 }
 
+static void GL_BINDING_CALL CustomReadPixels(
+    GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
+    GLenum type, void* pixels) {
+  GLenum gl_type = GetTexType(type);
+  return g_driver_gl.orig_fn.glReadPixelsFn(
+      x, y, width, height, format, gl_type, pixels);
+}
+
 }  // anonymous namespace
 
 void DriverGL::Initialize() {
   InitializeBindings();
 }
 
 void DriverGL::InitializeExtensions(GLContext* context) {
   InitializeExtensionBindings(context);
   orig_fn = fn;
   fn.glTexImage2DFn =
       reinterpret_cast<glTexImage2DProc>(CustomTexImage2D);
   fn.glTexSubImage2DFn =
       reinterpret_cast<glTexSubImage2DProc>(CustomTexSubImage2D);
   fn.glTexStorage2DEXTFn =
       reinterpret_cast<glTexStorage2DEXTProc>(CustomTexStorage2DEXT);
+  fn.glReadPixelsFn =
+      reinterpret_cast<glReadPixelsProc>(CustomReadPixels);
 }
 
 void InitializeGLBindingsGL() {
   g_driver_gl.Initialize();
   if (!g_real_gl) {
     g_real_gl = new RealGLApi();
     g_trace_gl = new TraceGLApi(g_real_gl);
   }
   g_real_gl->Initialize(&g_driver_gl);
   g_gl = g_real_gl;
@@ skipping 153 matching lines @@
 const GLubyte* VirtualGLApi::glGetStringFn(GLenum name) {
   switch (name) {
     case GL_EXTENSIONS:
       return reinterpret_cast<const GLubyte*>(extensions_.c_str());
     default:
       return driver_->fn.glGetStringFn(name);
   }
 }
 
 }  // namespace gfx