Move compositor InputHandler from RenderViewImpl to RenderWidget.

content/browser/renderer_host/render_widget_host_input_event_router.cc

 // Copyright 2015 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/render_widget_host_input_event_router.h"
 
 #include <vector>
 
 #include "base/metrics/histogram_macros.h"
 
@@ skipping 341 matching lines @@
       break;
     }
     case blink::WebInputEvent::TouchMove:
       if (touch_target_.target) {
         TransformEventTouchPositions(event, touch_target_.delta);
         touch_target_.target->ProcessTouchEvent(*event, latency);
       }
       break;
     case blink::WebInputEvent::TouchEnd:
     case blink::WebInputEvent::TouchCancel:
+      // It might be safer to test active_touches_ and only decrement it if it's
+      // non-zero, since active_touches_ can be reset to 0 in
+      // OnRenderWidgetHostViewBaseDestroyed, and this can happen between the
+      // TouchStart and a subsequent TouchMove/End/Cancel.
       DCHECK(active_touches_);
       active_touches_ -= CountChangedTouchPoints(*event);
       if (!touch_target_.target)
         return;
 
       TransformEventTouchPositions(event, touch_target_.delta);
       touch_target_.target->ProcessTouchEvent(*event, latency);
       if (!active_touches_)
         touch_target_.target = nullptr;
       break;
@@ skipping 403 matching lines @@
   if (!touchpad_gesture_target_.target)
     return;
 
   // TODO(mohsen): Add tests to check event location.
   event->x += touchpad_gesture_target_.delta.x();
   event->y += touchpad_gesture_target_.delta.y();
   touchpad_gesture_target_.target->ProcessGestureEvent(*event, latency);
 }
 
 }  // namespace content