Switch from plugin to browser process only when all windows close (Mac)
Switch from plugin to browser process only when all windows close (Mac)

Whenever a plugin-opened window is closed, check for other visible windows and only reactive the browser process if there aren't any.

BUG=23566
TEST=Press command-shift-G on a plugin-opened open dialog, then dismiss the sheet. The open dialog should stay visible and active.

Review URL: http://codereview.chromium.org/328013

git-svn-id: http://src.chromium.org/svn/trunk/src@29957 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: e3907a5c9af9f8573520c2980ba7aaab26b8b680
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser