Add knowledge about blocking and passive event listeners.

third_party/WebKit/public/platform/WebEventListenerProperties.h

Index: third_party/WebKit/public/platform/WebEventListenerProperties.h
diff --git a/third_party/WebKit/public/platform/WebEventListenerProperties.h b/third_party/WebKit/public/platform/WebEventListenerProperties.h
index 56ec72fd5e317a52069c8b8329fb5cb9710ef525..1b2d9a05402f8d817e9b9b2f2d8fa7207aa669ec 100644
--- a/third_party/WebKit/public/platform/WebEventListenerProperties.h
+++ b/third_party/WebKit/public/platform/WebEventListenerProperties.h
@@ -17,8 +17,9 @@ enum class WebEventListenerClass {
 // Indicates the variety of event listener types for a given WebEventListenerClass.
 enum class WebEventListenerProperties {
     Nothing, // This should be "None"; but None #defined in X11's X.h
-    Passive,
-    Blocking, // This indicates >= 1 blocking listener (and >= 0 passive listeners)
+    Passive, // This indicates solely passive listeners.
+    Blocking, // This indicates solely blocking listeners.
+    BlockingAndPassive, // This indicates >= 1 blocking listener and >= 1 passive listeners.
 };
 
 } // namespace blink