Communicate whether passive event listeners exist to cc.

cc/layers/layer_impl.cc

 // Copyright 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 "cc/layers/layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
@@ skipping 536 matching lines @@
             gfx::ToRoundedPoint(hit_test_point_in_layer_space))) {
       TRACE_EVENT0("cc",
                    "LayerImpl::tryScroll: Failed NonFastScrollableRegion");
       scroll_status.thread = InputHandler::SCROLL_ON_MAIN_THREAD;
       scroll_status.main_thread_scrolling_reasons =
           MainThreadScrollingReason::kNonFastScrollableRegion;
       return scroll_status;
     }
   }
 
-  if ((type == InputHandler::WHEEL || type == InputHandler::ANIMATED_WHEEL) &&
-      layer_tree_impl_->have_wheel_event_handlers()) {
-    TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed WheelEventHandlers");
-    scroll_status.thread = InputHandler::SCROLL_ON_MAIN_THREAD;
-    scroll_status.main_thread_scrolling_reasons =
-        MainThreadScrollingReason::kEventHandlers;
-    return scroll_status;
+  if (type == InputHandler::WHEEL || type == InputHandler::ANIMATED_WHEEL) {
+    EventListenerProperties event_properties =
+        layer_tree_impl_->event_listener_properties(
+            EventListenerClass::kMouseWheel);
+    if (event_properties == EventListenerProperties::kBlocking ||
+        (!layer_tree_impl_->settings().use_mouse_wheel_gestures &&
+         event_properties == EventListenerProperties::kPassive)) {
+      TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed WheelEventHandlers");
+      scroll_status.thread = InputHandler::SCROLL_ON_MAIN_THREAD;
+      scroll_status.main_thread_scrolling_reasons =
+          MainThreadScrollingReason::kEventHandlers;
+      return scroll_status;
+    }
   }
 
   if (!scrollable()) {
     TRACE_EVENT0("cc", "LayerImpl::tryScroll: Ignored not scrollable");
     scroll_status.thread = InputHandler::SCROLL_IGNORED;
     scroll_status.main_thread_scrolling_reasons =
         MainThreadScrollingReason::kNotScrollable;
     return scroll_status;
   }
 
@@ skipping 1333 matching lines @@
            .layer_transforms_should_scale_layer_contents) {
     return default_scale;
   }
 
   gfx::Vector2dF transform_scales = MathUtil::ComputeTransform2dScaleComponents(
       DrawTransform(), default_scale);
   return std::max(transform_scales.x(), transform_scales.y());
 }
 
 }  // namespace cc