Adding tracing to measure synthetic smooth scrolling correctness

BUG=162926

Review URL: https://chromiumcodereview.appspot.com/11413199

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@170642 0039d316-1c4b-4281-b951-d872f2087c98

cc/scrollbar_animation_controller.cc

@@ -4,6 +4,7 @@
 
 #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"
@@ -80,6 +81,12 @@ void ScrollbarAnimationController::updateScrollOffsetAtTime(LayerImpl* scrollLay
     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());
+
+
     if (m_horizontalScrollbarLayer) {
         m_horizontalScrollbarLayer->setCurrentPos(m_currentOffset.x());
         m_horizontalScrollbarLayer->setTotalSize(m_totalSize.width());

content/browser/renderer_host/render_widget_host_view_base.cc

@@ -4,6 +4,7 @@
 
 #include "content/browser/renderer_host/render_widget_host_view_base.h"
 
+#include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
@@ -460,6 +461,9 @@ class BasicMouseWheelSmoothScrollGesture
 
     pixels_scrolled_ += abs(event.deltaY);
 
+    TRACE_COUNTER_ID1("gpu", "smooth_scroll_by_pixels_scrolled", this,
+                      pixels_scrolled_);
+
     return true;
   }