Adding handlers for user gesture callbacks.

public/web/WebUserGestureIndicator.h

Index: public/web/WebUserGestureIndicator.h
diff --git a/public/web/WebUserGestureIndicator.h b/public/web/WebUserGestureIndicator.h
index b7c7f3cfcf1da8abd31c6af2cd8fef7b65e31ea4..b6ff87cd6d48d6334a39a2180dd03931ab347cd3 100644
--- a/public/web/WebUserGestureIndicator.h
+++ b/public/web/WebUserGestureIndicator.h
@@ -37,6 +37,12 @@ namespace blink {
 
 class WebUserGestureToken;
 
+class WebUserGestureHandler {
+public:
+    virtual ~WebUserGestureHandler() { }
+    virtual void onGesture() = 0;
+};
+
 class WebUserGestureIndicator {
 public:
     // Returns true if a user gesture is currently being processed.
@@ -49,6 +55,8 @@ public:
     // continue processing the user gesture later on using a
     // WebScopedUserGesture.
     BLINK_EXPORT static WebUserGestureToken currentUserGestureToken();
+
+    BLINK_EXPORT static void addHandler(WebUserGestureHandler*);
 };
 
 }