SyncFS: Implement FindNearestActiveAncestor


BUG=240165
TEST=unit_tests --gtest_filter=MetadataDatabaseTest.FindNearestActiveAncestor

Review URL: https://codereview.chromium.org/90173003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237576 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237576
Use ScopedMessagePipeHande in Connector.
This is the first step in moving the bindings entirely to
ScopedMessagePipeHandle

BUG=None
R=viettrungluu@chromium.org, viettrungluu

Review URL: https://codereview.chromium.org/89003003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237577 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237577