Pull methods upwards from ChromeTabCreator.

Pull methods upwards from ChromeTabCreator.

Pulls methods from the Impl into the Interface so that
ChromeActivity can take in a generic TabCreator instead of
a ChromeTabCreator implementation.

This is prep work for making it so that document mode's TabDelegate is also a TabCreator, which will let it be
usable in webapp mode for handling window.open calls.

BUG=451453
Committed: https://crrev.com/ae9ed0ff595735197f9e4042a844be0324da92dd
Cr-Commit-Position: refs/heads/master@{#333094}

[gone, 2015-06-05 01:18:27]

dfalcantara@chromium.org changed reviewers:
+ dtrainor@chromium.org

[gone, 2015-06-05 01:18:27]

Dave: I put some TODOs in here to explain what's going to be happening with this
class.  I plan to at least have the TabDelegate subclass, but I haven't decided
on what other methods I'll be pulling up or sending back down (loadUrl(), for
example, is just a utility function).

[David Trainor- moved to gerrit, 2015-06-05 05:38:19]

lgtm

[gone, 2015-06-05 15:36:53]

The CQ bit was checked by dfalcantara@chromium.org

[commit-bot: I haz the power, 2015-06-05 15:37:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1163173002/1

[commit-bot: I haz the power, 2015-06-05 16:12:21]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-05 16:12:22]

Try jobs failed on following builders:
  linux_android_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_android_r...)

[gone, 2015-06-05 17:46:59]

The CQ bit was checked by dfalcantara@chromium.org

[gone, 2015-06-05 17:46:59]

The patchset sent to the CQ was uploaded after l-g-t-m from
dtrainor@chromium.org
Link to the patchset: https://codereview.chromium.org/1163173002/#ps40001
(title: "Fixed the rebase")

[commit-bot: I haz the power, 2015-06-05 17:50:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1163173002/40001

[commit-bot: I haz the power, 2015-06-05 18:24:31]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-06-05 18:35:14]

Patchset 3 (id:??) landed as
https://crrev.com/ae9ed0ff595735197f9e4042a844be0324da92dd
Cr-Commit-Position: refs/heads/master@{#333094}