Implemented failIfMajorPerformanceCaveat WebGL context creation attribute.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 2b792130c00fe8cfa55c2bff58e1790879ceacc6..ecb1b9f233b26d9608196b2dedaa2c6b0c14bc99 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2281,6 +2281,20 @@ bool GLES2DecoderImpl::Initialize(
   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) {