Fix wheel scrolling over scrollbar not scrolling page.

third_party/WebKit/Source/core/input/EventHandler.cpp

Index: third_party/WebKit/Source/core/input/EventHandler.cpp
diff --git a/third_party/WebKit/Source/core/input/EventHandler.cpp b/third_party/WebKit/Source/core/input/EventHandler.cpp
index 645d51be8477559971abd6939f700eb84dfff90a..4b399f13e7b682a937ae32bfecce58c3e14d6b54 100644
--- a/third_party/WebKit/Source/core/input/EventHandler.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandler.cpp
@@ -1798,6 +1798,10 @@ WebInputEventResult EventHandler::handleWheelEvent(const PlatformWheelEvent& eve
     if (node && node->isTextNode())
         node = FlatTreeTraversal::parent(*node);
 
+    // If we're over a scrollbar, scroll the document.

[jbroman, 2016/03/16 15:41:00]

Just the (root?) frame scrollbars, right? Presumably hitting an overflow
scrollbar shouldn't scroll the document.

(I'm not familiar with what HitTestResult::innerNode will be in such cases, so I
don't know if this is just a question about the comment, or also the code.)

[bokan, 2016/03/16 18:01:45]

Yah, if it's over an overflow div innerNode will have the associated Node. I've
updated the comment.

+    if (!node && result.scrollbar())
+        node = doc->documentElement();
+
     bool sendDOMEvent = true;
     LocalFrame* subframe = subframeForTargetNode(node);
     if (subframe) {