Move PageState to FrameNavigationEntry.

Move PageState to FrameNavigationEntry.

This will allow us to store frame-specific states in --site-per-process,
which is necessary to support back/forward in out-of-process iframes.

BUG=236848
TEST=No behavior change.

Committed: https://crrev.com/44a0941b338626983b5215cfce34ce64eac84a85
Cr-Commit-Position: refs/heads/master@{#333224}

[Charlie Reis, 2015-06-05 23:37:07]

creis@chromium.org changed reviewers:
+ avi@chromium.org

[Charlie Reis, 2015-06-05 23:37:09]

This is just some prep work for subframe back/forward.  It's mostly a no-op for
now, but we can start putting frame-specific PageStates on
FrameNavigationEntries (in --site-per-process mode) once the manual subframe CL
finally lands.  Having PageState on FNE will be necessary for moving
HistoryController::GoToEntry to the browser process.

[Avi (use Gerrit), 2015-06-06 02:48:10]

lgtm

[Charlie Reis, 2015-06-07 02:44:17]

The CQ bit was checked by creis@chromium.org

[commit-bot: I haz the power, 2015-06-07 02:44:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1156733003/1

[commit-bot: I haz the power, 2015-06-07 03:37:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-07 03:38:07]

Patchset 1 (id:??) landed as
https://crrev.com/44a0941b338626983b5215cfce34ce64eac84a85
Cr-Commit-Position: refs/heads/master@{#333224}