RendererGLContext supports reparenting a GL context.

content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc

Index: content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc
===================================================================
--- content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc	(revision 89700)
+++ content/renderer/gpu/webgraphicscontext3d_command_buffer_impl.cc	(working copy)
@@ -104,6 +104,7 @@
   if (web_view && web_view->mainFrame())
     active_url = GURL(web_view->mainFrame()->url());
 
+  RendererGLContext* parent_context = NULL;
   if (render_directly_to_web_view) {
     RenderView* renderview = RenderView::FromWebView(web_view);
     if (!renderview)
@@ -125,7 +126,6 @@
   } else {
     bool compositing_enabled = !CommandLine::ForCurrentProcess()->HasSwitch(
         switches::kDisableAcceleratedCompositing);
-    RendererGLContext* parent_context = NULL;
     // If GPU compositing is enabled we need to create a GL context that shares
     // resources with the compositor's context.
     if (compositing_enabled) {
@@ -142,7 +142,6 @@
     }
     context_ = RendererGLContext::CreateOffscreenContext(
         host,
-        parent_context,
         gfx::Size(1, 1),
         preferred_extensions,
         attribs,
@@ -152,6 +151,9 @@
   if (!context_)
     return false;
 
+  if (!context_->SetParent(parent_context))
+    return false;
+
   gl_ = context_->GetImplementation();
   context_->SetContextLostCallback(
       NewCallback(this,