Only setup distillability mojo if needed

Only setup distillability mojo if needed

Prevent extra calls to set up mojo for Reader Mode's distillability
logic. Currently the distillability service is set up for any
RenderFrameHost that changes (this is not necessarily the main frame)
and even if the old service is still alive. This change starts
watching for when the service is killed and avoids service setup on
non-main frame hosts.

BUG=623979
Review-Url: https://codereview.chromium.org/2131343002
Cr-Commit-Position: refs/heads/master@{#404678}
(cherry picked from commit 70bb9fd22cc806498fc63a5749fdaaaea7354564)

Committed: https://chromium.googlesource.com/chromium/src/+/74bcb27419c3d35e16fffc977ceb32466f5d53b8

[wychen, 2016-07-30 00:36:02]

Description was changed from

==========
Only setup distillability mojo if needed

Prevent extra calls to set up mojo for Reader Mode's distillability
logic. Currently the distillability service is set up for any
RenderFrameHost that changes (this is not necessarily the main frame)
and even if the old service is still alive. This change starts
watching for when the service is killed and avoids service setup on
non-main frame hosts.

BUG=623979

Review-Url: https://codereview.chromium.org/2131343002
Cr-Commit-Position: refs/heads/master@{#404678}
(cherry picked from commit 70bb9fd22cc806498fc63a5749fdaaaea7354564)
==========

to

==========
Only setup distillability mojo if needed

Prevent extra calls to set up mojo for Reader Mode's distillability
logic. Currently the distillability service is set up for any
RenderFrameHost that changes (this is not necessarily the main frame)
and even if the old service is still alive. This change starts
watching for when the service is killed and avoids service setup on
non-main frame hosts.

BUG=623979

Review-Url: https://codereview.chromium.org/2131343002
Cr-Commit-Position: refs/heads/master@{#404678}
(cherry picked from commit 70bb9fd22cc806498fc63a5749fdaaaea7354564)

Committed:
https://chromium.googlesource.com/chromium/src/+/74bcb27419c3d35e16fffc977ceb...
==========

[wychen, 2016-07-30 00:36:03]

Committed patchset #1 (id:1) manually as
74bcb27419c3d35e16fffc977ceb32466f5d53b8.