Refactor frame detach to work for both local and remote frames.

Refactor frame detach to work for both local and remote frames.

BUG=346764
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179424

[dcheng, 2014-07-30 16:48:02]

I haven't quite figured out the story for frame detach but I think this is a
step in the right direction. For example, frame detach could be driven in two
different ways:
1) Browser initiated: the user closes a tab. We can probably rely on
~WebViewImpl running in all renderers to automatically detach the frames
associated with the page.
2) Renderer initiated: JS removes a frame from the DOM. In this case, it's
possible we could take advantage of WebFrameClient::frameDetached() signal that
we get in the embedder to relay that the corresponding frame in all other
renderers should be detached as well. WebFrameClient (or the browser process)
will have to get some understanding of when it needs to relay/when it doesn't
need to relay the signal though, so we don't end up in infinite loop. There may
also be potential issues with conflict resolution in the browser view of the
frame tree.

Furthermore, I haven't considered how this is going to work with WebFrame::swap
yet. We almost certainly need to call detach() on the Frame being swapped, since
LocalFrame expects certain code to always run before its destructor runs. But
it's also not clear when a good time for that is, since we also copy a bunch of
members off the WebFrame/Frame being swapped out.

Because of the potential complexity of these issues, I've opted to leave them
for followup patches.

[dcheng, 2014-07-31 17:24:48]

Ping?

[eseidel, 2014-08-01 21:42:46]

lgtm

[commit-bot: I haz the power, 2014-08-01 21:43:14]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dcheng@chromium.org/419863004/20001

[commit-bot: I haz the power, 2014-08-01 22:25:41]

Change committed as 179424