Migrate wheel events to EventHandlerRegistry

Source/core/frame/LocalFrame.cpp

Index: Source/core/frame/LocalFrame.cpp
diff --git a/Source/core/frame/LocalFrame.cpp b/Source/core/frame/LocalFrame.cpp
index e321c337713b91e0a6dec4724b374546a099a56d..b85d66f48929e44b335adc731a96698d63a84935 100644
--- a/Source/core/frame/LocalFrame.cpp
+++ b/Source/core/frame/LocalFrame.cpp
@@ -33,7 +33,6 @@
 #include "RuntimeEnabledFeatures.h"
 #include "bindings/v8/ScriptController.h"
 #include "core/dom/DocumentType.h"
-#include "core/dom/WheelController.h"
 #include "core/editing/Editor.h"
 #include "core/editing/FrameSelection.h"
 #include "core/editing/InputMethodController.h"
@@ -43,6 +42,7 @@
 #include "core/events/Event.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/frame/DOMWindow.h"
+#include "core/frame/EventHandlerRegistry.h"
 #include "core/frame/FrameConsole.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
@@ -507,13 +507,16 @@ void LocalFrame::deviceOrPageScaleFactorChanged()
 
 void LocalFrame::notifyChromeClientWheelEventHandlerCountChanged() const
 {
+    // TODO(skyostil): No-one is using this information, so remove this code.
     // Ensure that this method is being called on the main frame of the page.
     ASSERT(isMainFrame());
 
-    unsigned count = 0;
-    for (const LocalFrame* frame = this; frame; frame = frame->tree().traverseNext()) {
-        if (frame->document())
-            count += WheelController::from(*frame->document())->wheelEventHandlerCount();
+    EventHandlerRegistry& registry = m_host->eventHandlerRegistry();
+    unsigned count = registry.externalEventHandlerCount(EventHandlerRegistry::WheelEvent);
+    const EventTargetSet* targets = registry.eventHandlerTargets(EventHandlerRegistry::WheelEvent);
+    if (targets) {

[ojan, 2014/06/02 21:23:04]

There's no official style rule, but we typically do the following:
if (const EventTargetSet* targets =
registry.eventHandlerTargets(EventHandlerRegistry::WheelEvent))

It scopes the variable to the if clause and since you're declaring the variable
here, there's no possibility of silly bugs by accidentally typing == or
something like that.

[Sami, 2014/06/03 15:57:45]

Ah yes, that's a good idea. Done.

+        for (EventTargetSet::const_iterator iter = targets->begin(); iter != targets->end(); ++iter)
+            count += iter->value;
     }
 
     m_host->chrome().client().numWheelEventHandlersChanged(count);