Revert middle click related changes

third_party/WebKit/Source/core/events/MouseEvent.cpp

Index: third_party/WebKit/Source/core/events/MouseEvent.cpp
diff --git a/third_party/WebKit/Source/core/events/MouseEvent.cpp b/third_party/WebKit/Source/core/events/MouseEvent.cpp
index f6a378fe3618ce1e66108b507106a9fd1a914af9..77e22e2fbff9203f84dcd29a7b5c229a2ed92978 100644
--- a/third_party/WebKit/Source/core/events/MouseEvent.cpp
+++ b/third_party/WebKit/Source/core/events/MouseEvent.cpp
@@ -293,10 +293,6 @@ DispatchEventResult MouseEventDispatchMediator::dispatchEvent(EventDispatcher& d
     if (mouseEvent.type() != EventTypeNames::click || mouseEvent.detail() != 2)
         return dispatchResult;
 
-    // Do not send dblclick event for non-primary button clicks.
-    if (mouseEvent.button() != MouseButton::LeftButton)
-        return dispatchResult;
-
     // Special case: If it's a double click event, we also send the dblclick event. This is not part
     // of the DOM specs, but is used for compatibility with the ondblclick="" attribute. This is treated
     // as a separate event in other DOM-compliant browsers like Firefox, and so we do the same.