Make bookmark related tests not flaky

Make bookmark related tests not flaky

BookmarksBridgeTest and EnhancedBookmarksModelTest are no longer chrome
shell tests. They are now running as NativeLibraryTest and have much
shorter initialization time. Therefore there are great chances that the
model is not loaded when getMobileFolderId() is called.

This CL adds criteria to check whether the bridge has loaded or not, and
pause the UI thread for a while.

BUG=515489
Committed: https://crrev.com/7f79a1dbe726730103b4a814cc291eb0f661201e
Cr-Commit-Position: refs/heads/master@{#342144}

[Ian Wen, 2015-08-06 00:35:56]

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

[Ian Wen, 2015-08-06 00:35:57]

Since Ted is OOO, Dan, as a rock star in java testing, could you ptal? :P

[gone, 2015-08-06 17:05:19]

Your message drips with sarcasm, but lgtm :P

[Ian Wen, 2015-08-06 17:13:43]

The CQ bit was checked by ianwen@chromium.org

[commit-bot: I haz the power, 2015-08-06 17:14:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1268403004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1268403004/1

[commit-bot: I haz the power, 2015-08-06 17:48:43]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-06 17:49:56]

Patchset 1 (id:??) landed as
https://crrev.com/7f79a1dbe726730103b4a814cc291eb0f661201e
Cr-Commit-Position: refs/heads/master@{#342144}

[Kibeom Kim (inactive), 2015-08-06 18:04:20]

kkimlabs@chromium.org changed reviewers:
+ kkimlabs@chromium.org

[Kibeom Kim (inactive), 2015-08-06 18:04:20]

minor point: I think it's better to listen bookmark model loaded event by an
observer because there is a default timeout for polling so not guaranteed.
Though probably wouldn't fail in practice so I think it's OK for now.