Disable the idle handler timer when no action is expected.

On Android, the webkit timer are disabled after the application is in
the background for 5 minutes. When this happens, there is no reason to
let the idle handler timer run indefinitly. This CL disables the timer
once v8 reported that it will not take any further action.

BUG=333875

Review URL: https://codereview.chromium.org/136903002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245908 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245908
Files.app: Remove DEFAULT_MOUNT_PATH.

After introducing per-profile paths, the download directory is no longer
'/Downloads'.

BUG=336101
TEST=manually

Review URL: https://codereview.chromium.org/141513003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245909 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245909