Move Content Service off Service Manager

This sticks a Content Service instance directly in each BrowserContext
rather than having them owned indirectly by BrowserContext via
Service Manager APIs.

The two existing uses are refactored to get NavigableContentsFactory
receivers bound directly through the BrowserContext rather than using
a Service Manager Connector.

Bug: 977637
Change-Id: I4a3e41235e15a8b93973f152e8313d8612bfc290
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1931444
Commit-Queue: Ken Rockot <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Reviewed-by: Robert Sesek <[email protected]>
Reviewed-by: Xiyuan Xia <[email protected]>
Cr-Commit-Position: refs/heads/master@{#721729}
28 files changed