Flash players weren't receiving mouse wheel events.

third_party/WebKit/Source/web/WebPluginContainerImpl.cpp

Index: third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp b/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
index 08a0799da30733a8419d489946114b62866e9fd5..94dd414b43a53ec522dacc5a7761d08f80312801 100644
--- a/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
+++ b/third_party/WebKit/Source/web/WebPluginContainerImpl.cpp
@@ -548,8 +548,8 @@ void WebPluginContainerImpl::requestTouchEventType(TouchEventRequestType request
     if (m_touchEventRequestType == requestType || !m_element)
         return;
 
-    if (m_element->document().frameHost()) {
-        EventHandlerRegistry& registry = m_element->document().frameHost()->eventHandlerRegistry();
+    if (FrameHost* frameHost = m_element->document().frameHost()) {
+        EventHandlerRegistry& registry = frameHost->eventHandlerRegistry();
         if (requestType != TouchEventRequestTypeNone && m_touchEventRequestType == TouchEventRequestTypeNone)
             registry.didAddEventHandler(*m_element, EventHandlerRegistry::TouchEventBlocking);
         else if (requestType == TouchEventRequestTypeNone && m_touchEventRequestType != TouchEventRequestTypeNone)
@@ -562,6 +562,14 @@ void WebPluginContainerImpl::setWantsWheelEvents(bool wantsWheelEvents)
 {
     if (m_wantsWheelEvents == wantsWheelEvents)
         return;
+    if (FrameHost* frameHost = m_element->document().frameHost()) {
+        EventHandlerRegistry& registry = frameHost->eventHandlerRegistry();
+        if (wantsWheelEvents)
+            registry.didAddEventHandler(*m_element, EventHandlerRegistry::WheelEventBlocking);
+        else
+            registry.didRemoveEventHandler(*m_element, EventHandlerRegistry::WheelEventBlocking);
+    }
+
     m_wantsWheelEvents = wantsWheelEvents;
     if (Page* page = m_element->document().page()) {
         if (ScrollingCoordinator* scrollingCoordinator = page->scrollingCoordinator()) {
@@ -720,6 +728,10 @@ void WebPluginContainerImpl::dispose()
     m_isDisposed = true;
 
     requestTouchEventType(TouchEventRequestTypeNone);
+    if (m_element && m_wantsWheelEvents) {
+        if (FrameHost* frameHost = m_element->document().frameHost())
+            frameHost->eventHandlerRegistry().didRemoveEventHandler(*m_element, EventHandlerRegistry::WheelEventBlocking);

[aelias_OOO_until_Jul13, 2016/03/24 19:15:05]

Can we call "setWantsWheelEvents(false);" to avoid the code duplication?

[dtapuska, 2016/03/24 21:14:29]

I wanted to avoid the updateGeometry call inside the setWantsWheelEvents method.
But I could break apart that method into a helper function I could call from
dispose. Also for some reason the build bots aren't liking this change for the
tests. Will have to look at it Tuesday.

[aelias_OOO_until_Jul13, 2016/03/25 00:05:40]

Why did you want that, is there a reason to think calling updateGeometry() will
cause a problem?  If it's just for performance, sounds like premature
optimization, since I'd be surprised if WebPluginContainerImpl::dispose() was on
any kind of critical path.

+    }
 
     if (m_webPlugin) {
         RELEASE_ASSERT(!m_webPlugin->container() || m_webPlugin->container() == this);