MimeHandlerViewGuest: Ignore title changes due to navigations.

MimeHandlerViewGuest: Ignore title changes due to navigations.

Currently, when a mime handler is loaded, the URL of the mime handler is
used as the embedder's title. This causes that title to flicker between
the URL of the content, the URL of the mime handler and the title set by
the mime handler. This changes MimeHandlerViewGuest to only update the
embedder's title when the mime handler's title changes without the URL
also changing.

BUG=47914
Committed: https://crrev.com/3493265a42600578d77e75a398c0659c301c5228
Cr-Commit-Position: refs/heads/master@{#358778}

[Sam McNally, 2015-11-04 02:58:02]

Patchset #1 (id:1) has been deleted

[Sam McNally, 2015-11-04 06:47:08]

Patchset #2 (id:40001) has been deleted

[Sam McNally, 2015-11-04 06:50:02]

sammc@chromium.org changed reviewers:
+ raymes@chromium.org

[Sam McNally, 2015-11-10 02:04:19]

PTAL

[raymes, 2015-11-10 02:07:39]

lgtm

[Sam McNally, 2015-11-10 03:14:26]

The CQ bit was checked by sammc@chromium.org

[commit-bot: I haz the power, 2015-11-10 03:15:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1431713004/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1431713004/60001

[commit-bot: I haz the power, 2015-11-10 03:21:27]

Committed patchset #2 (id:60001)

[commit-bot: I haz the power, 2015-11-10 03:22:46]

Patchset 2 (id:??) landed as
https://crrev.com/3493265a42600578d77e75a398c0659c301c5228
Cr-Commit-Position: refs/heads/master@{#358778}