Introduce PPB_Flash_MessageLoop interface for Pepper Flash.

      Comparing with PPB_Flash.RunMessageLoop/QuitMessageLoop, this new interface avoids leaking nested message loops. If Quit() is not called to balance the call to Run(), the outermost message loop will be quitted when the resource is destroyed.

BUG=109340
TEST=test_flash_message_loop.{h,cc}


Review URL: http://codereview.chromium.org/9188045

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@119873 0039d316-1c4b-4281-b951-d872f2087c98