Remove drive-status-changed event.

The only client of drive-status-changed was FileListBannerController. It can
be replaced by alternative implementation based on splice event on volume info
list.

BUG=268817
TEST=Ran browser_tests --gtest_filter="*FileSystemExtensionApiTest*:*FileManagerBrowserTest*:*FileBrowserPrivateApiTest*" and tested manually.

Review URL: https://codereview.chromium.org/25214002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226186 0039d316-1c4b-4281-b951-d872f2087c98
Remove Valgrind suppression added in r225935.

The uninitialized read has been fixed.

TBR=glider@chromium.org
BUG=301500

Review URL: https://codereview.chromium.org/25460002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226187 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226186
SVN changes up to revision 226187