Android: Factor InProductHelp UI out of Tab

This CL moves the methods handling InProductHelp UI in Tab to
ToolbarButtonInProductHelpController using ActivityLifecycleDispatcher and
Tab page load observing mechanism. Now the methods are handled by
ChromeTabbedActivity only.

Bug: 889682
Change-Id: Idce805f60f32ad90418c0f6e3ded80df6d18f9b1
Reviewed-on: https://chromium-review.googlesource.com/c/1272779
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609881}
3 files changed