Files.app: Dispatch 'drive-connection-changed' event on initialization of VolumeManagerWrapper.
VolumeManagerWrapper.getDriveConnectionState() returns 'offline' until the instance of VolumeManagerWrapper is wired to background's VolumeManager.
Since the return value can be changed when it is wired to VolumeManager, we need to notify foreground components so that they update themselves based on the latest connection status.
BUG=509565
TEST=manually
Review URL: https://codereview.chromium.org/
1240583002
Cr-Commit-Position: refs/heads/master@{#338648}