Add Page Based Scroll main thread scrolling reason.

ui/events/blink/input_handler_proxy.cc

 // Copyright 2013 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 "ui/events/blink/input_handler_proxy.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 415 matching lines @@
           ? -wheel_event.deltaX
           : 0,
       wheel_event.railsMode != WebInputEvent::RailsModeHorizontal
           ? -wheel_event.deltaY
           : 0);
 
   if (wheel_event.scrollByPage) {
     // TODO(jamesr): We don't properly handle scroll by page in the compositor
     // thread, so punt it to the main thread. http://crbug.com/236639
     result = DID_NOT_HANDLE;
+    RecordMainThreadScrollingReasons(wheel_event.type,
+                                     cc::InputHandler::PAGE_BASED_SCROLLING);
+
   } else if (!wheel_event.canScroll) {
     // Wheel events with |canScroll| == false will not trigger scrolling,
     // only event handlers.  Forward to the main thread.
     result = DID_NOT_HANDLE;
   } else if (ShouldAnimate(wheel_event)) {
     cc::InputHandler::ScrollStatus scroll_status =
         input_handler_->ScrollAnimated(gfx::Point(wheel_event.x, wheel_event.y),
                                        scroll_delta);
 
     RecordMainThreadScrollingReasons(
@@ skipping 699 matching lines @@
   // trigger a scroll, e.g., with a trivial time delta between fling updates.
   // Return true in this case to prevent early fling termination.
   if (std::abs(clipped_increment.width) < kScrollEpsilon &&
       std::abs(clipped_increment.height) < kScrollEpsilon)
     return true;
 
   return did_scroll;
 }
 
 }  // namespace ui