[Telemetry] Merge _PageState to _RunState in page_runner.py

Merge _PageState to _RunState in page_runner.py

The motivation behind this merge is to create a single place
that manages the browser & tab state before running multiple
page, before running each page, after running each page, and
after running multiple pages. Next patches will refactor
this _RunState object to SharedPageState as planned in
https://docs.google.com/a/google.com/document/d/1on2ATPE8Y7a0SLcd4cl3nAiSthVpVLU6OoVZatEavEA/edit.

Besides the merging of PageState and RunState, this patch
also renames _RunPage -> _RunPageAndProcessErrorIfNeeded
and _PrepareAndRunPage -> _RunPageAndRetryRunIfNeeded to
clear up the distinction what each of these functions does.

BUG=418278
Committed: https://crrev.com/32943ec796c9c235fae4048b00a73bb3fcd140f9
Cr-Commit-Position: refs/heads/master@{#299425}

[nednguyen, 2014-10-13 20:28:04]

Patchset #1 (id:1) has been deleted

[nednguyen, 2014-10-13 20:28:10]

Patchset #1 (id:30001) has been deleted

[nednguyen, 2014-10-13 20:40:16]

nednguyen@google.com changed reviewers:
+ dtu@chromium.org, tonyg@chromium.org

[dtu, 2014-10-14 00:08:30]

lgtm

[nednguyen, 2014-10-14 01:24:45]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2014-10-14 01:27:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/652813002/50001

[commit-bot: I haz the power, 2014-10-14 03:50:55]

Committed patchset #1 (id:50001)

[commit-bot: I haz the power, 2014-10-14 03:51:36]

Patchset 1 (id:??) landed as
https://crrev.com/32943ec796c9c235fae4048b00a73bb3fcd140f9
Cr-Commit-Position: refs/heads/master@{#299425}