Defer render_widget draw until host window is available

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index b76e2a8a26c6df7b90b193639497dd4a0a1f6333..64f294a5a9ef076c28987e153eb29a127dca9177 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -4495,12 +4495,21 @@ 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) {