Adding tracing to measure synthetic smooth scrolling correctness

cc/scrollbar_animation_controller.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_animation_controller.h"
 
+#include "base/debug/trace_event.h"
 #include "base/time.h"
 #include "build/build_config.h"
 #include "cc/scrollbar_layer_impl.h"
 
 #if defined(OS_ANDROID)
 #include "cc/scrollbar_animation_controller_linear_fade.h"
 #endif
 
 namespace cc {
 
@@ skipping 56 matching lines @@
     // a cleaner way to get the contentBounds on the Impl side.
     return scrollLayer->children()[0]->bounds();
 }
 
 void ScrollbarAnimationController::updateScrollOffsetAtTime(LayerImpl* scrollLayer, double)
 {
     m_currentOffset = scrollLayer->scrollOffset() + scrollLayer->scrollDelta();
     m_totalSize = getScrollLayerBounds(scrollLayer);
     m_maximum = scrollLayer->maxScrollOffset();
 
+    // Get the m_currentOffset.y() value for a sanity-check on scrolling
+    // benchmark metrics. Specifically, we want to make sure
+    // BasicMouseWheelSmoothScrollGesture has proper scroll curves.
+    TRACE_COUNTER_ID1("gpu", "scroll_offset_y", this, m_currentOffset.y());

[nduca, 2013/01/04 22:42:13]

we should be passing a layerTreeHostImpl pointer here.

+
+
     if (m_horizontalScrollbarLayer) {
         m_horizontalScrollbarLayer->setCurrentPos(m_currentOffset.x());
         m_horizontalScrollbarLayer->setTotalSize(m_totalSize.width());
         m_horizontalScrollbarLayer->setMaximum(m_maximum.x());
     }
 
     if (m_verticalScrollbarLayer) {
         m_verticalScrollbarLayer->setCurrentPos(m_currentOffset.y());
         m_verticalScrollbarLayer->setTotalSize(m_totalSize.height());
         m_verticalScrollbarLayer->setMaximum(m_maximum.y());
     }
 }
 
 }  // namespace cc