--- a/dom/plugins/base/nsNPAPIPluginInstance.cpp
+++ b/dom/plugins/base/nsNPAPIPluginInstance.cpp
@@ -666,17 +666,18 @@ nsresult nsNPAPIPluginInstance::Print(NP
   platformPrint->print.embedPrint.window.clipRect.top,
   platformPrint->print.embedPrint.window.clipRect.bottom,
   platformPrint->print.embedPrint.window.clipRect.left,
   platformPrint->print.embedPrint.window.clipRect.right));
 
   return NS_OK;
 }
 
-nsresult nsNPAPIPluginInstance::HandleEvent(void* event, int16_t* result)
+nsresult nsNPAPIPluginInstance::HandleEvent(void* event, int16_t* result,
+                                            NSPluginCallReentry aSafeToReenterGecko)
 {
   if (RUNNING != mRunning)
     return NS_OK;
 
   if (!event)
     return NS_ERROR_FAILURE;
 
   PluginDestructionGuard guard(this);
@@ -687,17 +688,17 @@ nsresult nsNPAPIPluginInstance::HandleEv
   NPPluginFuncs* pluginFunctions = mPlugin->PluginFuncs();
 
   int16_t tmpResult = kNPEventNotHandled;
 
   if (pluginFunctions->event) {
     mCurrentPluginEvent = event;
 #if defined(XP_WIN) || defined(XP_OS2)
     NS_TRY_SAFE_CALL_RETURN(tmpResult, (*pluginFunctions->event)(&mNPP, event), this,
-                            NS_PLUGIN_CALL_UNSAFE_TO_REENTER_GECKO);
+                            aSafeToReenterGecko);
 #else
     MAIN_THREAD_JNI_REF_GUARD;
     tmpResult = (*pluginFunctions->event)(&mNPP, event);
 #endif
     NPP_PLUGIN_LOG(PLUGIN_LOG_NOISY,
       ("NPP HandleEvent called: this=%p, npp=%p, event=%p, return=%d\n", 
       this, &mNPP, event, tmpResult));
 

--- a/dom/plugins/base/nsNPAPIPluginInstance.h
+++ b/dom/plugins/base/nsNPAPIPluginInstance.h
@@ -82,17 +82,18 @@ public:
   NS_DECL_ISUPPORTS
 
   nsresult Initialize(nsNPAPIPlugin *aPlugin, nsPluginInstanceOwner* aOwner, const char* aMIMEType);
   nsresult Start();
   nsresult Stop();
   nsresult SetWindow(NPWindow* window);
   nsresult NewStreamFromPlugin(const char* type, const char* target, nsIOutputStream* *result);
   nsresult Print(NPPrint* platformPrint);
-  nsresult HandleEvent(void* event, int16_t* result);
+  nsresult HandleEvent(void* event, int16_t* result,
+                       NSPluginCallReentry aSafeToReenterGecko = NS_PLUGIN_CALL_UNSAFE_TO_REENTER_GECKO);
   nsresult GetValueFromPlugin(NPPVariable variable, void* value);
   nsresult GetDrawingModel(int32_t* aModel);
   nsresult IsRemoteDrawingCoreAnimation(bool* aDrawing);
   nsresult ContentsScaleFactorChanged(double aContentsScaleFactor);
   nsresult GetJSObject(JSContext *cx, JSObject** outObject);
   bool ShouldCache();
   nsresult IsWindowless(bool* isWindowless);
   nsresult AsyncSetWindow(NPWindow* window);

--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -2061,17 +2061,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
       pluginWidget->EndDrawPlugin();
       return nsEventStatus_eIgnore;
     }
   }
 
   int16_t response = kNPEventNotHandled;
   void* window = FixUpPluginWindow(ePluginPaintEnable);
   if (window || (eventModel == NPEventModelCocoa)) {
-    mInstance->HandleEvent(event, &response);
+    mInstance->HandleEvent(event, &response, NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
   }
 
   if (eventModel == NPEventModelCocoa && response == kNPEventStartIME) {
     pluginWidget->StartComplexTextInputForCurrentEvent();
   }
 
   if ((response == kNPEventHandled || response == kNPEventStartIME) &&
       !(anEvent.eventStructType == NS_MOUSE_EVENT &&
@@ -2177,17 +2177,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
   if (pPluginEvent && !pPluginEvent->event) {
     // Don't send null events to plugins.
     NS_WARNING("nsObjectFrame ProcessEvent: trying to send null event to plugin.");
     return rv;
   }
 
   if (pPluginEvent) {
     int16_t response = kNPEventNotHandled;
-    mInstance->HandleEvent(pPluginEvent, &response);
+    mInstance->HandleEvent(pPluginEvent, &response, NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
     if (response == kNPEventHandled)
       rv = nsEventStatus_eConsumeNoDefault;
   }
 #endif
 
 #ifdef MOZ_X11
   // this code supports windowless plugins
   nsIWidget* widget = anEvent.widget;
@@ -2435,17 +2435,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
   event.display = widget ?
     static_cast<Display*>(widget->GetNativeData(NS_NATIVE_DISPLAY)) : nullptr;
   event.window = None; // not a real window
   // information lost:
   event.serial = 0;
   event.send_event = False;
 
   int16_t response = kNPEventNotHandled;
-  mInstance->HandleEvent(&pluginEvent, &response);
+  mInstance->HandleEvent(&pluginEvent, &response, NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
   if (response == kNPEventHandled)
     rv = nsEventStatus_eConsumeNoDefault;
 #endif
 
 #ifdef MOZ_WIDGET_ANDROID
   // this code supports windowless plugins
   {
     // The plugin needs focus to receive keyboard and touch events
@@ -2487,44 +2487,44 @@ nsEventStatus nsPluginInstanceOwner::Pro
           case NS_MOUSE_BUTTON_DOWN:
             {
               ANPEvent event;
               event.inSize = sizeof(ANPEvent);
               event.eventType = kMouse_ANPEventType;
               event.data.mouse.action = kDown_ANPMouseAction;
               event.data.mouse.x = pluginPoint.x;
               event.data.mouse.y = pluginPoint.y;
-              mInstance->HandleEvent(&event, nullptr);
+              mInstance->HandleEvent(&event, nullptr, NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
             }
             break;
           case NS_MOUSE_BUTTON_UP:
             {
               ANPEvent event;
               event.inSize = sizeof(ANPEvent);
               event.eventType = kMouse_ANPEventType;
               event.data.mouse.action = kUp_ANPMouseAction;
               event.data.mouse.x = pluginPoint.x;
               event.data.mouse.y = pluginPoint.y;
-              mInstance->HandleEvent(&event, nullptr);
+              mInstance->HandleEvent(&event, nullptr, NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
             }
             break;
           }
       }
       break;
 
     case NS_KEY_EVENT:
      {
        const nsKeyEvent& keyEvent = static_cast<const nsKeyEvent&>(anEvent);
        LOG("Firing NS_KEY_EVENT %d %d\n", keyEvent.keyCode, keyEvent.charCode);
        // pluginEvent is initialized by nsWindow::InitKeyEvent().
        ANPEvent* pluginEvent = reinterpret_cast<ANPEvent*>(keyEvent.pluginEvent);
        if (pluginEvent) {
          MOZ_ASSERT(pluginEvent->inSize == sizeof(ANPEvent));
          MOZ_ASSERT(pluginEvent->eventType == kKey_ANPEventType);
-         mInstance->HandleEvent(pluginEvent, nullptr);
+         mInstance->HandleEvent(pluginEvent, nullptr, NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
        }
      }
      break;
 
     default:
       break;
     }
     rv = nsEventStatus_eConsumeNoDefault;