Add GL_EXT_color_buffer_half_float support

gpu/command_buffer/service/context_group.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 "gpu/command_buffer/service/context_group.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 34 matching lines @@
     adjusted_disallowed_features.npot_support = true;
     adjusted_disallowed_features.oes_texture_half_float_linear = true;
   }
   if (context_type == CONTEXT_TYPE_WEBGL1 ||
       context_type == CONTEXT_TYPE_WEBGL2) {
     adjusted_disallowed_features.chromium_color_buffer_float_rgba = true;
     adjusted_disallowed_features.chromium_color_buffer_float_rgb = true;
     adjusted_disallowed_features.ext_color_buffer_float = true;
     adjusted_disallowed_features.oes_texture_float_linear = true;
   }
+  if (context_type == CONTEXT_TYPE_WEBGL2) {
+    adjusted_disallowed_features.ext_color_buffer_half_float = true;

[Zhenyao Mo, 2017/02/23 05:49:10]

This also needs to be disallowed for WebGL1 because the extension has to be
explicitly enabled later.

+  }
   return adjusted_disallowed_features;
 }
 
 }  // namespace anonymous
 
 ContextGroup::ContextGroup(
     const GpuPreferences& gpu_preferences,
     const scoped_refptr<MailboxManager>& mailbox_manager,
     const scoped_refptr<MemoryTracker>& memory_tracker,
     const scoped_refptr<ShaderTranslatorCache>& shader_translator_cache,
@@ skipping 563 matching lines @@
     GLuint client_id, GLuint* service_id) const {
   Buffer* buffer = buffer_manager_->GetBuffer(client_id);
   if (!buffer)
     return false;
   *service_id = buffer->service_id();
   return true;
 }
 
 }  // namespace gles2
 }  // namespace gpu