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 9c7c90abb22c2dd86abcd750000c19291588bd9a..88b65e12350f3c1cc9d366a28ffcebb3de5e9e3d 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -778,8 +778,10 @@ 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

[dcheng, 2017/01/12 10:19:21]

This comment is a bit confusing to me. I assume "chrome" here means the chrome
ui, and if I weren't familiar with OOPIF, I would be wondering why this comment
mentions this outer/inner web contents concept at all.

Also, I would imagine this is also used when focus transitions between
cross-process frames, right?

Perhaps wording the comment to be a more generic would be nice:
When the renderer needs the browser to transfer focus cross-process on its
behalf in the focus hierarchy. This may focus an element in the browser ui or a
cross-process frame, as appropriate.

[avallee, 2017/01/12 20:00:23]

Done.

+// WebContents to continue focus traversal after the element representing the
+// inner WebContents.
 IPC_MESSAGE_ROUTED1(ViewHostMsg_TakeFocus,
                     bool /* reverse */)