Allow vibrate in cross-origin iframes with user gesture.

third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp

Index: third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
diff --git a/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp b/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
index 77c0ce17a2369290356d15bd872b5cb3c38f69a3..51addbc90670baf84d2bf1a3799a8cde87a8257d 100644
--- a/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
+++ b/third_party/WebKit/Source/modules/vibration/NavigatorVibration.cpp
@@ -88,8 +88,9 @@ bool NavigatorVibration::vibrate(Navigator& navigator,
           "frame.");
     } else {
       frame->domWindow()->printErrorMessage(
-          "A call of navigator.vibrate will be no-op inside cross-origin "
-          "iframes: https://www.chromestatus.com/feature/5682658461876224.");
+          "A call of navigator.vibrate will be no-op inside a cross-origin "
+          "iframe if there is no user activation on the iframe: "
+          "https://www.chromestatus.com/feature/5682658461876224.");
     }
     return false;
   }