Retry 3 to split WebGraphicsContext3DCommandBufferImpl::initialize() into two stages.

content/renderer/gpu/renderer_gl_context.cc

Index: content/renderer/gpu/renderer_gl_context.cc
diff --git a/content/renderer/gpu/renderer_gl_context.cc b/content/renderer/gpu/renderer_gl_context.cc
index 6320c80b9bb4aaaea7461b0da175ccc143393a93..255bd13f708cd3f29eae525f7d14bab37e6e5693 100644
--- a/content/renderer/gpu/renderer_gl_context.cc
+++ b/content/renderer/gpu/renderer_gl_context.cc
@@ -199,6 +199,7 @@ void RendererGLContext::SetContextLostCallback(
 
 bool RendererGLContext::MakeCurrent(RendererGLContext* context) {
   if (context) {
+    DCHECK(context->CalledOnValidThread());
     gles2::SetGLContext(context->gles2_implementation_);
 
     // Don't request latest error status from service. Just use the locally
@@ -290,6 +291,7 @@ bool RendererGLContext::Initialize(bool onscreen,
                                    const char* allowed_extensions,
                                    const int32* attrib_list,
                                    const GURL& active_url) {
+  DCHECK(CalledOnValidThread());
   DCHECK(size.width() >= 0 && size.height() >= 0);
   TRACE_EVENT2("gpu", "RendererGLContext::Initialize",
                    "on_screen", onscreen, "num_pixels", size.GetArea());
@@ -413,6 +415,7 @@ bool RendererGLContext::Initialize(bool onscreen,
 
 void RendererGLContext::Destroy() {
   TRACE_EVENT0("gpu", "RendererGLContext::Destroy");
+  DCHECK(CalledOnValidThread());
   SetParent(NULL);
 
   if (gles2_implementation_) {