Fix cross-window focus in Chrome Frame.

Fix cross-window focus in Chrome Frame.

Text input wasn't working due to requirements of the IME/TSF machinery
that weren't being met by ExternalTabContainerWin.

* ExternalTabContainerWin now provides an implementation for
  WebContentsDelegate::WebContentsFocused that calls into its WebView's
  OnWebContentsFocused method. This mimics BrowserView, and permits
  proper focus tracking via the FocusManager.

* ExternalTabContainerWin now provides a specialization of
  DesktopRootWindowHostWin that saves and restores focus on blur/focus
  events. The stock DRWHW does this based on window activation, but this
  doesn't work for ETCW since the ETCW's DRWHW doesn't receive
  activation messages due to it being a child of an IE window rather
  than a top-level window.

* IEEventSink::SendKeys now sets focus to the renderer before sending
  key down/up messages.

BUG=241081
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=202270

[grt (UTC plus 2), 2013-05-24 18:41:15]

sky: chrome/browser/ui/views
erikwright: chrome_frame

Please redirect as appropriate. Thanks.

[erikwright (departed), 2013-05-24 18:56:49]

chrome_frame LGTM.

[sky, 2013-05-24 20:25:53]

LGTM

[commit-bot: I haz the power, 2013-05-24 22:10:23]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/grt@chromium.org/15944007/2001

[commit-bot: I haz the power, 2013-05-25 03:48:25]

Retried try job too often on linux_chromeos for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_chro...

[commit-bot: I haz the power, 2013-05-25 12:03:29]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/grt@chromium.org/15944007/2001

[commit-bot: I haz the power, 2013-05-25 13:58:31]

Change committed as 202270