Telemetry: Ensure a single scroll gesture & measure smoothness during gesture only.

This patch removes the mechanism for doing multiple scroll gestures in
scroll.js, because it introduced noise. The number of scrolls could change
from one run to the next, depending on whether JS values had been updated in
time or not.

The patch also adds a trace event that's fired at the beginning and end of a
gesture inside the synthetic gesture controller. When computing the GPU
rendering stats, only events that happened during the gesture are considered.
This improves upon the previous implementation which relied on trace data
recorded from JS.
This method relies on there only being a single gesture (hence the change
above).

BUG=265901

Review URL: https://chromiumcodereview.appspot.com/23532057

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224422 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 6 insertions, 0 deletions

diff --git a/content/browser/renderer_host/synthetic_gesture_controller.cc b/content/browser/renderer_host/synthetic_gesture_controller.cc
index d066f0f..46c4329 100644
--- a/content/browser/renderer_host/synthetic_gesture_controller.cc
+++ b/content/browser/renderer_host/synthetic_gesture_controller.cc
@@ -40,6 +40,8 @@ void SyntheticGestureController::BeginSmoothScroll(
       params.mouse_event_x,
       params.mouse_event_y);
 
+  TRACE_EVENT_ASYNC_BEGIN0("benchmark", "SyntheticGestureController::running",
+      pending_synthetic_gesture_);
   timer_.Start(FROM_HERE, GetSyntheticGestureMessageInterval(), this,
                &SyntheticGestureController::OnTimer);
 }
@@ -57,6 +59,8 @@ void SyntheticGestureController::BeginPinch(
       params.anchor_x,
       params.anchor_y);
 
+  TRACE_EVENT_ASYNC_BEGIN0("benchmark", "SyntheticGestureController::running",
+      pending_synthetic_gesture_);
   timer_.Start(FROM_HERE, GetSyntheticGestureMessageInterval(), this,
                &SyntheticGestureController::OnTimer);
 }
@@ -70,6 +74,8 @@ void SyntheticGestureController::OnTimer() {
   base::TimeTicks now = base::TimeTicks::Now();
   if (!pending_synthetic_gesture_->ForwardInputEvents(now, rwh_)) {
     timer_.Stop();
+    TRACE_EVENT_ASYNC_END0("benchmark", "SyntheticGestureController::running",
+        pending_synthetic_gesture_);
     pending_synthetic_gesture_ = NULL;
     rwh_->Send(new ViewMsg_SyntheticGestureCompleted(rwh_->GetRoutingID()));
   }