Implemented failIfMajorPerformanceCaveat WebGL context creation attribute.

gpu/command_buffer/service/gles2_cmd_decoder.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/gles2_cmd_decoder.h"
 
 #include <stdio.h>
 
 #include <algorithm>
 #include <list>
@@ skipping 2263 matching lines @@
     state_.texture_units[tt].bound_texture_2d = ref;
     glBindTexture(GL_TEXTURE_2D, ref->service_id());
   }
   glActiveTexture(GL_TEXTURE0);
   CHECK_GL_ERROR();
 
   ContextCreationAttribHelper attrib_parser;
   if (!attrib_parser.Parse(attribs))
     return false;
 
+  // If the failIfMajorPerformanceCaveat context creation attribute was true
+  // and we are using a software renderer, fail.
+  if (attrib_parser.fail_if_major_perf_caveat_) {
+    CommandLine* command_line = CommandLine::ForCurrentProcess();
+    if (command_line->HasSwitch(switches::kUseGL)) {

[Zhenyao Mo, 2013/11/20 22:44:57]

You don't have to check here.  If kUseGL is not there, it simply returns an
empty string.

Also, why don't we move this and the attrib_parser to the top of the function?
so we don't waste work if it's swiftshader.

+      std::string requested_implementation_name =
+          command_line->GetSwitchValueASCII(switches::kUseGL);
+      if (requested_implementation_name == "swiftshader") {

[piman, 2013/11/20 22:44:55]

Can we move the logic about "is this swiftshader" into the feature_info.cc,
maybe even feeding this through the bug/workarounds blacklist?

+        Destroy(true);
+        return false;

[Ken Russell (switch to Gerrit), 2013/11/20 22:39:02]

How has this been tested?

+      }
+    }
+  }
+
   if (offscreen) {
     if (attrib_parser.samples_ > 0 && attrib_parser.sample_buffers_ > 0 &&
         features().chromium_framebuffer_multisample) {
       // Per ext_framebuffer_multisample spec, need max bound on sample count.
       // max_sample_count must be initialized to a sane value.  If
       // glGetIntegerv() throws a GL error, it leaves its argument unchanged.
       GLint max_sample_count = 1;
       glGetIntegerv(GL_MAX_SAMPLES_EXT, &max_sample_count);
       offscreen_target_samples_ = std::min(attrib_parser.samples_,
                                            max_sample_count);
@@ skipping 8217 matching lines @@
   DoDidUseTexImageIfNeeded(texture, texture->target());
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu