Don't use tests requiring BROWSER_CLOSED notifications on Mac.
Don't use tests requiring BROWSER_CLOSED notifications on Mac.

Browser closes must be done in the top level message loop on Mac, so
tests that rely on the close completing (e.g. wait for notification of it)
can't be done on that platform.  See comment in
BrowserWindowController::windowWillClose for details.

BUG=None
TEST=browser_tests --gtest_filter=DownloadTest.* --gtest_also_run_disabled_tests

Review URL: http://codereview.chromium.org/6246153

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@74147 0039d316-1c4b-4281-b951-d872f2087c98

adobe/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,yitian134/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,ropik/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,adobe/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,ropik/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,ropik/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium