Bug 1461708 - part 3: EventStateManager::InitAndDispatchClickEvent() shouldn't overwrite nsEventStatus with nsEventStatus_eIgnore r=smaug

EventStateManager::InitAndDispatchClickEvent() sends given nsEventStatus to
nsIPresShell::HandleEventWithTarget().  Then, it sends the status to
EventStateManager::PreHandleEvent() before dispatching the event.  At this
time, EventStateManager::PreHandleEvent() resets the state to
nsEventStatus_eIgnore.  Therefore, for example, if eMouseClick event is
consumed but eMouseAuxClick is ignored, the event status result is
nsEventStatus_eIgnore.  So, neither DispatchClickEvents() nor
PostMouseUpEventHandler() cannot check whether at least one click event
is consumed.

This patch makes EventStateManager::InitAndDispatchClickEvent() sends
local variable of nsEventStatus to nsIPresShell::HandleEventWithTarget().
Then, merge the result with current status.

If we'd change nsEventStatus to enum class, we could make this change as
custom "operator|=" or something.

Differential Revision: https://phabricator.services.mozilla.com/D7850

--HG--
extra : moz-landing-system : lando

dom/events/EventStateManager.cpp

@@ -5008,8 +5008,26 @@ EventStateManager::InitAndDispatchClickEvent(WidgetMouseEvent* aMouseUpEvent,
     targetFrame = aOverrideClickTarget->GetPrimaryFrame();
   }
 
-  return aPresShell->HandleEventWithTarget(&event, targetFrame,
-                                           target, aStatus);
+  // Use local event status for each click event dispatching since it'll be
+  // cleared by EventStateManager::PreHandleEvent().  Therefore, dispatching
+  // an event means that previous event status will be ignored.
+  nsEventStatus status = nsEventStatus_eIgnore;
+  nsresult rv = aPresShell->HandleEventWithTarget(&event, targetFrame,
+                                                  target, &status);
+  // If current status is nsEventStatus_eConsumeNoDefault, we don't need to
+  // overwrite it.
+  if (*aStatus == nsEventStatus_eConsumeNoDefault) {
+    return rv;
+  }
+  // If new status is nsEventStatus_eConsumeNoDefault or
+  // nsEventStatus_eConsumeDoDefault, use it.
+  if (status == nsEventStatus_eConsumeNoDefault ||
+      status == nsEventStatus_eConsumeDoDefault) {
+    *aStatus = status;
+    return rv;
+  }
+  // Otherwise, keep the original status.
+  return rv;
 }
 
 nsresult

dom/events/EventStateManager.h

@@ -469,6 +469,9 @@ protected:
    *                                EventCausesClickEvents() must return true
    *                                if this event is set to it.
    * @param aStatus                 Returns the result of click event.
+   *                                If the status indicates consumed, the
+   *                                value won't be overwritten with
+   *                                nsEventStatus_eIgnore.
    * @param aMessage                Should be eMouseClick, eMouseDoubleClick or
    *                                eMouseAuxClick.
    * @param aPresShell              The PresShell.