Mouse event handlers use user gesture tokens on top-level LocalFrames.

Source/core/frame/LocalFrame.cpp

Index: Source/core/frame/LocalFrame.cpp
diff --git a/Source/core/frame/LocalFrame.cpp b/Source/core/frame/LocalFrame.cpp
index 2e322cefd8fdf2ed767b3d9cdf91c9f018960732..d1f6be381ab3a6a7cf2f139d07cec2a35d5e7d4a 100644
--- a/Source/core/frame/LocalFrame.cpp
+++ b/Source/core/frame/LocalFrame.cpp
@@ -616,4 +616,13 @@ void LocalFrame::disconnectOwnerElement()
     Frame::disconnectOwnerElement();
 }
 
+LocalFrame* LocalFrame::localFrameRoot()
+{
+    LocalFrame* curFrame = this;
+    while (curFrame && curFrame->tree().parent() && curFrame->tree().parent()->isLocalFrame())
+        curFrame = curFrame->tree().parent();
+
+    return curFrame;
+}
+
 } // namespace WebCore