Telemtry: hooks "chrome.gpuBenchmarking.smoothScrollBy" with java on android.

content/browser/renderer_host/basic_mouse_wheel_smooth_scroll_gesture.cc

 // Copyright (c) 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 "content/browser/renderer_host/basic_mouse_wheel_smooth_scroll_gesture.h"
 
 #include "base/debug/trace_event.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 
 namespace content {
 
 BasicMouseWheelSmoothScrollGesture::BasicMouseWheelSmoothScrollGesture(
     bool scroll_down, int pixels_to_scroll,
     int mouse_event_x, int mouse_event_y)
     : scroll_down_(scroll_down),
       pixels_scrolled_(0),
       pixels_to_scroll_(pixels_to_scroll),
       mouse_event_x_(mouse_event_x),
       mouse_event_y_(mouse_event_y) { }
 
 BasicMouseWheelSmoothScrollGesture::~BasicMouseWheelSmoothScrollGesture() { }
 
 bool BasicMouseWheelSmoothScrollGesture::ForwardInputEvents(
     base::TimeTicks now, RenderWidgetHost* host) {
 
   if (pixels_scrolled_ >= pixels_to_scroll_)
     return false;
 
-  double positionDelta = 10;
-  if (!last_tick_time_.is_null()) {
-    RenderWidgetHostImpl* hostImpl = RenderWidgetHostImpl::From(host);
-    double desiredIntervalMs = hostImpl->SyntheticScrollMessageInterval();
-    double velocity = 10 / desiredIntervalMs;
-    double timeDelta = (now - last_tick_time_).InMillisecondsF();
-    positionDelta = velocity * timeDelta;
-  }
-
-  last_tick_time_ = now;
+  double position_delta = Tick(
+      now, RenderWidgetHostImpl::From(host)->SyntheticScrollMessageInterval());
 
   WebKit::WebMouseWheelEvent event;
   event.type = WebKit::WebInputEvent::MouseWheel;
   event.hasPreciseScrollingDeltas = 1;
-  event.deltaY = scroll_down_ ? -positionDelta : positionDelta;
+  event.deltaY = scroll_down_ ? -position_delta : position_delta;
   // TODO(vollick): find a proper way to access
   // WebCore::WheelEvent::tickMultiplier.
   event.wheelTicksY = event.deltaY / 120;
   event.modifiers = 0;
 
   // TODO(nduca): Figure out plausible x and y values.
   event.globalX = 0;
   event.globalY = 0;
   event.x = mouse_event_x_;
   event.y = mouse_event_y_;
   event.windowX = event.x;
   event.windowY = event.y;
   host->ForwardWheelEvent(event);
 
   pixels_scrolled_ += abs(event.deltaY);
 
   TRACE_COUNTER_ID1(
       "gpu", "smooth_scroll_by_pixels_scrolled", this, pixels_scrolled_);
 
   return true;
 }
 
 }  // content