Defer compositor context creation to the thread.

cc/output/context_provider.h

Index: cc/output/context_provider.h
diff --git a/cc/output/context_provider.h b/cc/output/context_provider.h
index 2245b643e134b464d0db441cd4bd5dfae0ca2d2e..0ebb02eb13e0668fc59600525fce167512fcef12 100644
--- a/cc/output/context_provider.h
+++ b/cc/output/context_provider.h
@@ -57,13 +57,15 @@ class ContextProvider : public base::RefCountedThreadSafe<ContextProvider> {
     base::AutoLock context_lock_;
   };
 
-  // Bind the 3d context to the current thread. This should be called before
-  // accessing the contexts. Calling it more than once should have no effect.
-  // Once this function has been called, the class should only be accessed
-  // from the same thread unless the function has some explicitly specified
-  // rules for access on a different thread. See SetupLockOnMainThread(), which
-  // can be used to provide access from multiple threads.
-  virtual bool BindToCurrentThread() = 0;
+  // This Factory class allows deferred creation of a context provider (for eg.
+  // on another thread than the main thread).
+  class Factory {
+   public:
+    // Creates and returns a new context provider. The context provider may only
+    // be used on the thread it is created on unless it supports locking (via
+    // the ScopedContextLock class).
+    virtual scoped_refptr<ContextProvider> CreateContext() = 0;
+  };
 
   virtual gpu::gles2::GLES2Interface* ContextGL() = 0;
   virtual gpu::ContextSupport* ContextSupport() = 0;