[InputEvent] Add InputEvent with basic interface behind a flag

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

Index: third_party/WebKit/Source/core/events/Event.cpp
diff --git a/third_party/WebKit/Source/core/events/Event.cpp b/third_party/WebKit/Source/core/events/Event.cpp
index 9ea661ffbf59ef4f072c3f5cc3514fecc60ad2ee..375233706fb5ec0b1b73fe782cf2d498867013a2 100644
--- a/third_party/WebKit/Source/core/events/Event.cpp
+++ b/third_party/WebKit/Source/core/events/Event.cpp
@@ -184,6 +184,11 @@ bool Event::isPointerEvent() const
     return false;
 }
 
+bool Event::isInputEvent() const
+{
+    return false;
+}
+
 bool Event::isDragEvent() const
 {
     return false;