Defer render_widget draw until host window is available

content/renderer/render_view_impl.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 "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <string>
 #include <vector>
@@ skipping 4477 matching lines @@
        plugin_it != plugin_delegates_.end(); ++plugin_it) {
     (*plugin_it)->SetContainerVisibility(true);
   }
 #endif  // OS_MACOSX
 }
 
 bool RenderViewImpl::SupportsAsynchronousSwapBuffers() {
   if (WebWidgetHandlesCompositorScheduling())
     return false;
 
+  if (queried_for_swapbuffers_complete_callback_)
+    return context_has_swapbuffers_complete_callback_;

[piman, 2012/01/30 18:10:23]

I'm not sure caching this is a valid thing to do. This code is unfortunately
fairly subtle (and insufficiently tested) and it impacts the correctness of the
synchronization. But in the old code, I believe this value turns false when the
context is lost or we turn off accelerated compositing, and I think it's
necessary to keep that behavior.
Problems (such as the renderer stops drawing frames) can be reproduced by
killing the GPU process, or loading a page that keeps turning on and of
accelerated compositing.

+
+  queried_for_swapbuffers_complete_callback_ = true;
+
   WebKit::WebGraphicsContext3D* context = webview()->graphicsContext3D();
-  if (!context)
-    return false;
-  std::string extensions(context->getRequestableExtensionsCHROMIUM().utf8());
-  return extensions.find("GL_CHROMIUM_swapbuffers_complete_callback") !=
-      std::string::npos;
+  if (context) {
+    context->makeContextCurrent();
+    std::string extensions(context->getRequestableExtensionsCHROMIUM().utf8());
+    context_has_swapbuffers_complete_callback_ =
+        extensions.find("GL_CHROMIUM_swapbuffers_complete_callback")
+            != std::string::npos;
+  }
+
+  return context_has_swapbuffers_complete_callback_;
 }
 
 void RenderViewImpl::OnSetFocus(bool enable) {
   RenderWidget::OnSetFocus(enable);
 
   if (webview() && webview()->isActive()) {
     // Notify all NPAPI plugins.
     std::set<WebPluginDelegateProxy*>::iterator plugin_it;
     for (plugin_it = plugin_delegates_.begin();
          plugin_it != plugin_delegates_.end(); ++plugin_it) {
@@ skipping 434 matching lines @@
 bool RenderViewImpl::WebWidgetHandlesCompositorScheduling() const {
   return !!RenderThreadImpl::current()->compositor_thread();
 }
 
 void RenderViewImpl::OnJavaBridgeInit() {
   DCHECK(!java_bridge_dispatcher_.get());
 #if defined(ENABLE_JAVA_BRIDGE)
   java_bridge_dispatcher_.reset(new JavaBridgeDispatcher(this));
 #endif
 }