Hook ANGLE_request_extension up to the passthrough cmd decoder.

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc

 // Copyright (c) 2016 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/gles2_cmd_decoder_passthrough.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "ui/gl/gl_version_info.h"
 
 namespace gpu {
@@ skipping 2578 matching lines @@
 error::Error GLES2DecoderPassthroughImpl::DoResizeCHROMIUM(GLuint width,
                                                            GLuint height,
                                                            GLfloat scale_factor,
                                                            GLboolean alpha) {
   NOTIMPLEMENTED();
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoGetRequestableExtensionsCHROMIUM(
     const char** extensions) {
-  *extensions = "";
-  NOTIMPLEMENTED();
+  *extensions = reinterpret_cast<const char*>(
+      glGetString(GL_REQUESTABLE_EXTENSIONS_ANGLE));
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoRequestExtensionCHROMIUM(
     const char* extension) {
-  NOTIMPLEMENTED();
+  glRequestExtensionANGLE(extension);
+
+  // Make sure there are no pending GL errors before re-initializing feature
+  // info
+  FlushErrors();
+
+  // Make sure newly enabled extensions are exposed and usable.
+  context_->ReinitializeDynamicBindings();

[Zhenyao Mo, 2017/03/09 18:03:18]

This is potentially a perf concern for WebGL startup (they enable a bunch of
extensions at startup, each calling into this.

In theory, we can initialize all bindings unconditionally, and let validation
decide if a command is legitimate or not.

Could you at least add a TODO and maybe create a bug to look into this later?

[Geoff Lang, 2017/03/16 14:59:46]

Done, put a comment next to GLContext::ReinitializeDynamicBindings.

+  if (!feature_info_->Initialize(feature_info_->context_type(),
+                                 feature_info_->disallowed_features())) {
+    return error::kLostContext;
+  }
+
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoGetProgramInfoCHROMIUM(
     GLuint program,
     std::vector<uint8_t>* data) {
   GLuint service_program = 0;
   if (!resources_->program_id_map.GetServiceID(program, &service_program)) {
     return error::kNoError;
   }
@@ skipping 855 matching lines @@
     GLint x,
     GLint y,
     GLint width,
     GLint height) {
   NOTIMPLEMENTED();
   return error::kNoError;
 }
 
 }  // namespace gles2
 }  // namespace gpu