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

cc/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/scrollbar_layer.h"
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/caching_bitmap_content_layer_updater.h"
 #include "cc/layer_painter.h"
@@ skipping 250 matching lines @@
 
     // We should always have enough memory for UI.
     DCHECK(resource->texture()->canAcquireBackingTexture());
     if (!resource->texture()->canAcquireBackingTexture())
         return;
 
     // Paint and upload the entire part.
     gfx::Rect paintedOpaqueRect;
     painter->prepareToUpdate(rect, rect.size(), contentsScaleX(), contentsScaleY(), paintedOpaqueRect, stats);
     if (!painter->pixelsDidChange() && resource->texture()->haveBackingTexture()) {
-        TRACE_EVENT_INSTANT0("cc","ScrollbarLayer::updatePart no texture upload needed");
+        TRACE_EVENT_INSTANT0("cc", "ScrollbarLayer::updatePart no texture upload needed",
+                             TRACE_EVENT_SCOPE_THREAD);
         return;
     }
 
     bool partialUpdatesAllowed = layerTreeHost()->settings().maxPartialTextureUpdates > 0;
     if (!partialUpdatesAllowed)
         resource->texture()->returnBackingTexture();
 
     gfx::Vector2d destOffset(0, 0);
     resource->update(queue, rect, destOffset, partialUpdatesAllowed, stats);
 }
@@ skipping 52 matching lines @@
     gfx::Rect thumbRect = m_geometry->thumbRect(m_scrollbar.get());
     m_thumbSize = thumbRect.size();
     gfx::Rect originThumbRect = scrollbarLayerRectToContentRect(gfx::Rect(thumbRect.size()));
     if (!originThumbRect.IsEmpty())
         updatePart(m_thumbUpdater.get(), m_thumb.get(), originThumbRect, queue, stats);
 
     m_dirtyRect = gfx::RectF();
 }
 
 }  // namespace cc