Remove offscreen compositor contexts.

cc/trees/layer_tree_host_client.h

Index: cc/trees/layer_tree_host_client.h
diff --git a/cc/trees/layer_tree_host_client.h b/cc/trees/layer_tree_host_client.h
index deca8008f05fb13bc1f81dec3d2b5288bf627a14..bd185e87d1337d9d8d23bd80099d65bfee83b433 100644
--- a/cc/trees/layer_tree_host_client.h
+++ b/cc/trees/layer_tree_host_client.h
@@ -37,11 +37,6 @@ class LayerTreeHostClient {
   virtual void DidCommitAndDrawFrame() = 0;
   virtual void DidCompleteSwapBuffers() = 0;
 
-  // If the client provides an OutputSurface bound to a 3d context for direct
-  // rendering, this must return a provider that provides contexts usable from
-  // the same thread as the OutputSurface's context.
-  virtual scoped_refptr<ContextProvider> OffscreenContextProvider() = 0;
-
   // Requests that the client insert a rate limiting token in the shared main
   // thread context's command stream that will block if the context gets too far
   // ahead of the compositor's command stream. Only needed if the tree contains