Use Event::isTouchEvent() to prevent a bad cast

Bug: 11676314

Cherry pick https://codereview.chromium.org/32423007.

Change-Id: If0b43721975e32779726428954931e3d994a9409
diff --git a/Source/web/WebPluginContainerImpl.cpp b/Source/web/WebPluginContainerImpl.cpp
index 65d50f5..1b86221 100644
--- a/Source/web/WebPluginContainerImpl.cpp
+++ b/Source/web/WebPluginContainerImpl.cpp
@@ -192,7 +192,7 @@
         handleWheelEvent(static_cast<WheelEvent*>(event));
     else if (event->isKeyboardEvent())
         handleKeyboardEvent(toKeyboardEvent(event));
-    else if (eventNames().isTouchEventType(event->type()))
+    else if (event->isTouchEvent())
         handleTouchEvent(static_cast<TouchEvent*>(event));
     else if (eventNames().isGestureEventType(event->type()))
         handleGestureEvent(static_cast<GestureEvent*>(event));