Bug 1257759 part.5 PluginInstanceChild should post received native key event to chrome process if the key combination may be a shortcut key r=jimm

When PluginInstanceChild receives native key events, it should post the events to the chrome process first for checking if the key combination is reserved.  However, posting all key events to the chrome process may make damage to the performance of text input.  Therefore, this patch starts to post a key event whose key combination may be a shortcut key.  However, for avoiding to shuffle the event order, it posts following key events until all posted key events are handled by the chrome process.

For receiving response from widget, this patch defines nsIKeyEventInPluginCallback.  It's specified by nsIWidget::OnWindowedPluginKeyEvent() for ensuring the caller will receive the reply.  Basically, the caller of nsIWidget::OnWindowedPluginKeyEvent() should reply to the child process.  However, if the widget is a PuppetWidget, it cannot return the result synchronously.  Therefore, PuppetWidget::OnWindowedPluginKeyEvent() returns NS_SUCCESS_EVENT_HANDLED_ASYNCHRONOUSLY and stores the callback to mKeyEventInPluginCallbacks.  Then, TabParent::HandledWindowedPluginKeyEvent() will call PuppetWidget::HandledWindowedPluginKeyEvent().

MozReview-Commit-ID: G6brOU26NwQ

dom/plugins/ipc/PluginLibrary.h

@@ -91,6 +91,10 @@ public:
     virtual nsresult GetScrollCaptureContainer(NPP aInstance, mozilla::layers::ImageContainer** aContainer) = 0;
     virtual nsresult UpdateScrollState(NPP aInstance, bool aIsScrolling) = 0;
 #endif
+  virtual nsresult HandledWindowedPluginKeyEvent(
+                     NPP aInstance,
+                     const mozilla::NativeEventData& aNativeKeyData,
+                     bool aIsCOnsumed) = 0;
 
   /**
    * The next three methods are the third leg in the trip to