Add a |scope| argument to TRACE_EVENT_INSTANT* and require its presence.

cc/trees/layer_tree_host.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
@@ skipping 492 matching lines @@
 }
 
 void LayerTreeHost::SetNeedsAnimate() {
   DCHECK(proxy_->HasImplThread());
   proxy_->SetNeedsAnimate();
 }
 
 void LayerTreeHost::SetNeedsCommit() {
   if (!prepaint_callback_.IsCancelled()) {
     TRACE_EVENT_INSTANT0("cc",
-                         "LayerTreeHost::SetNeedsCommit::cancel prepaint");
+                         "LayerTreeHost::SetNeedsCommit::cancel prepaint",
+                         TRACE_EVENT_SCOPE_THREAD);
     prepaint_callback_.Cancel();
   }
   proxy_->SetNeedsCommit();
 }
 
 void LayerTreeHost::SetNeedsFullTreeSync() {
   needs_full_tree_sync_ = true;
   SetNeedsCommit();
 }
 
@@ skipping 523 matching lines @@
     SetAnimationEventsRecursive(events,
                                 layer->children()[child_index].get(),
                                 wall_clock_time);
 }
 
 skia::RefPtr<SkPicture> LayerTreeHost::CapturePicture() {
   return proxy_->CapturePicture();
 }
 
 }  // namespace cc