Communicate whether passive event listeners exist to cc.

cc/trees/layer_tree_host_impl_unittest.cc

 // Copyright 2011 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/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 699 matching lines @@
       ScrollInfoContains(*scroll_info, scroll_layer->id(), scroll_delta));
 }
 
 TEST_F(LayerTreeHostImplTest, ScrollBlocksOnWheelEventHandlers) {
   SetupScrollAndContentsLayers(gfx::Size(100, 100));
   host_impl_->SetViewportSize(gfx::Size(50, 50));
   DrawFrame();
 
   // With registered event handlers, wheel scrolls don't necessarily
   // have to go to the main thread.
-  host_impl_->active_tree()->set_have_wheel_event_handlers(true);
+  host_impl_->active_tree()->set_event_listener_properties(
+      EventListenerClass::kMouseWheel, EventListenerProperties::kBlocking);
   InputHandler::ScrollStatus status =
     host_impl_->ScrollBegin(BeginState(gfx::Point()).get(),
                                    InputHandler::WHEEL);
   EXPECT_EQ(InputHandler::SCROLL_ON_MAIN_THREAD, status.thread);
   EXPECT_EQ(MainThreadScrollingReason::kEventHandlers,
             status.main_thread_scrolling_reasons);
 
   // But gesture scrolls can still be handled.
   status = host_impl_->ScrollBegin(BeginState(gfx::Point()).get(),
                                    InputHandler::GESTURE);
   EXPECT_EQ(InputHandler::SCROLL_ON_IMPL_THREAD, status.thread);
   EXPECT_EQ(MainThreadScrollingReason::kNotScrollingOnMain,
             status.main_thread_scrolling_reasons);
   host_impl_->ScrollEnd(EndState().get());
 
   // And if the handlers go away, wheel scrolls can again be processed
   // on impl (despite the scroll-blocks-on mode).

[Rick Byers, 2016/02/04 22:18:57]

Looks like we missed updating the comment and test name when you removed
scroll-blocks-on.  I think the one above (L718) is probably also stale.  This
test probably should be renamed / reworked to be testing passive vs. active vs.
nothing wheel listener behavior.  But maybe you want to do that in your next CL
instead and just leave it confusing for now?

-  host_impl_->active_tree()->set_have_wheel_event_handlers(false);
+  host_impl_->active_tree()->set_event_listener_properties(
+      EventListenerClass::kMouseWheel, EventListenerProperties::kNone);
   status = host_impl_->ScrollBegin(BeginState(gfx::Point()).get(),
                                    InputHandler::WHEEL);
   EXPECT_EQ(InputHandler::SCROLL_ON_IMPL_THREAD, status.thread);
   EXPECT_EQ(MainThreadScrollingReason::kNotScrollingOnMain,
             status.main_thread_scrolling_reasons);
   host_impl_->ScrollEnd(EndState().get());
 }
 
 TEST_F(LayerTreeHostImplTest, ScrollBlocksOnTouchEventHandlers) {
   LayerImpl* scroll = SetupScrollAndContentsLayers(gfx::Size(100, 100));
@@ skipping 9212 matching lines @@
     // There should not be any jitter measured till we hit the fixed point hits
     // threshold.
     float expected_jitter =
         (i == pending_tree->kFixedPointHitsThreshold) ? 500 : 0;
     EXPECT_EQ(jitter, expected_jitter);
   }
 }
 
 }  // namespace
 }  // namespace cc