Prevent CopyOutputRequest from crashing when using surfaces.

It was hitting a DCHECK when attempting to copy the CopyOutputRequest whenever navigating between pages.

BUG=

Review URL: https://codereview.chromium.org/511603002

Cr-Commit-Position: refs/heads/master@{#292037}

content/browser/compositor/delegated_frame_host.cc

@@ -130,7 +130,12 @@ bool DelegatedFrameHost::ShouldCreateResizeLock() {
 
 void DelegatedFrameHost::RequestCopyOfOutput(
     scoped_ptr<cc::CopyOutputRequest> request) {
-  client_->GetLayer()->RequestCopyOfOutput(request.Pass());
+  if (use_surfaces_) {
+    // TODO(jbauman): Make this work with surfaces.
+    request->SendEmptyResult();
+  } else {
+    client_->GetLayer()->RequestCopyOfOutput(request.Pass());
+  }
 }
 
 void DelegatedFrameHost::CopyFromCompositingSurface(