Implement WebContentsViewChildFrame::TakeFocus.

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index b9d444dbfe04c8058556966598d374301c1dfb1a..5a0685d65f7497a0011cb3284408a0ab3e8f9380 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -789,8 +789,10 @@ IPC_MESSAGE_ROUTED2(ViewHostMsg_EnumerateDirectory,
                     int /* request_id */,
                     base::FilePath /* file_path */)
 
-// Tells the browser to move the focus to the next (previous if reverse is
-// true) focusable element.
+// Tells the browser to move the focus to the next (previous if reverse is true)
+// focusable element in chrome if this is the top-level view or tells an outer
+// WebContents to continue focus traversal after the element representing the
+// inner WebContents.
 IPC_MESSAGE_ROUTED1(ViewHostMsg_TakeFocus,
                     bool /* reverse */)