Add the button style for combobox

Added a new style for combobox, which enables the users to click the text part of a combobox.
Please see the screenshots at crbug/305494.

BUG=305494

Review URL: https://codereview.chromium.org/59383003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240057 0039d316-1c4b-4281-b951-d872f2087c98
Fix SyncFS v2 whitelisting code

Also add DumpDatabase support for per-origin v2 backend

BUG=324215
TEST=manual

Review URL: https://codereview.chromium.org/111603002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240058 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240057
Files.app: Make delete operation cancellable.

This CL adds a cancel callback to delete progress items, which allows user to
cancel the operation.

BUG=318928
TEST=invoke 2 delete tasks. Cancel them.

Review URL: https://codereview.chromium.org/103313003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240059 0039d316-1c4b-4281-b951-d872f2087c98
Remove legacy from drive::internal::FileCache.

- Remove XXXOnUIThread methods.
- Merge StoreInternal method to Store.

BUG=231221

Review URL: https://codereview.chromium.org/108873005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240060 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240060