[SyncFS] Wire up notifications to SyncEngine and implement state management

 * Setting up notification observers in SyncEngine
 * Kick ListChangesTask on notification.

R=kinuko, nhiroki
BUG=240165

Review URL: https://codereview.chromium.org/26567012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230983 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230983
Use CastEnvironment and CastSender in CastSessionDelegate

Implementing more of CastSessionDelegate by using CastEnvironment
and CastSender. CastEnvironment is now properly configured.

CastSender is now constructed but not configured correctly. This will
be done in upcoming changes.

BUG=301920

Review URL: https://codereview.chromium.org/34743002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230984 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230984