scheduler: Handle mouse wheel event disposition correctly

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

 // Copyright 2014 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 "platform/scheduler/renderer/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 626 matching lines @@
       break;
 
     case blink::WebInputEvent::MouseMove:
       // Consider mouse movement with the left button held down (see
       // ShouldPrioritizeInputEvent) similarly to a touch gesture.
       AnyThread().last_gesture_was_compositor_driven =
           input_event_state == InputEventState::EVENT_CONSUMED_BY_COMPOSITOR;
       AnyThread().awaiting_touch_start_response = false;
       break;
 
+    case blink::WebInputEvent::MouseWheel:
+      AnyThread().last_gesture_was_compositor_driven =
+          input_event_state == InputEventState::EVENT_CONSUMED_BY_COMPOSITOR;
+      AnyThread().awaiting_touch_start_response = false;
+      // If the event was sent to the main thread, assume the default gesture is
+      // prevented until we see evidence otherwise.
+      AnyThread().default_gesture_prevented =
+          !AnyThread().last_gesture_was_compositor_driven;
+      break;
+
     case blink::WebInputEvent::Undefined:
       break;
 
     default:
       AnyThread().awaiting_touch_start_response = false;
       break;
   }
 
   // Avoid unnecessary policy updates if the use case did not change.
   UseCase use_case = ComputeCurrentUseCase(now, &unused_policy_duration);
@@ skipping 929 matching lines @@
     case v8::PERFORMANCE_LOAD:
       return "load";
     default:
       NOTREACHED();
       return nullptr;
   }
 }
 
 }  // namespace scheduler
 }  // namespace blink