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

cc/layers/scrollbar_layer.cc

 // Copyright 2012 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/layers/scrollbar_layer.h"
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/layers/scrollbar_layer_impl.h"
 #include "cc/resources/caching_bitmap_content_layer_updater.h"
@@ skipping 320 matching lines @@
   gfx::Rect painted_opaque_rect;
   painter->PrepareToUpdate(rect,
                            rect.size(),
                            contents_scale_x(),
                            contents_scale_y(),
                            &painted_opaque_rect,
                            stats);
   if (!painter->pixels_did_change() &&
       resource->texture()->have_backing_texture()) {
     TRACE_EVENT_INSTANT0("cc",
-                         "ScrollbarLayer::UpdatePart no texture upload needed");
+                         "ScrollbarLayer::UpdatePart no texture upload needed",
+                         TRACE_EVENT_SCOPE_THREAD);
     return;
   }
 
   bool partial_updates_allowed =
       layer_tree_host()->settings().max_partial_texture_updates > 0;
   if (!partial_updates_allowed)
     resource->texture()->ReturnBackingTexture();
 
   gfx::Vector2d dest_offset(0, 0);
   resource->Update(queue, rect, dest_offset, partial_updates_allowed, stats);
@@ skipping 80 matching lines @@
                thumb_.get(),
                origin_thumb_rect,
                queue,
                stats);
   }
 
   dirty_rect_ = gfx::RectF();
 }
 
 }  // namespace cc