Web SQL: Make sure DatabaseManager is used only in the main thread.

Web SQL: Make sure DatabaseManager is used only in the main thread.

Only DatabaseManager::closeDatabasesImmediately could be called in non-main
threads. However, it just calls
DatabaseTracker::closeDatabasesImmediately(). This CL removes
DatabaseManager::closeDatabasesImmediately, and only the main thread uses
DatabaseManager.

So, we can remove DatabaseManager::m_contextMapLock.  We still need m_contextMap
because the main thread can have multiple Documents.

Oilpan: We can use PersistentHeapHashMap, and remove some |#if ENABLE(OILPAN)|.

BUG=347902, 397429
TEST=No new tests because of no behavior changes.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181810

[tkent, 2014-09-11 06:31:59]

tkent@chromium.org changed reviewers:
+ michaeln@chromium.org, oilpan-reviews@chromium.org

[tkent, 2014-09-11 06:32:00]

Please review this.

[Mads Ager (chromium), 2014-09-11 06:40:14]

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

[Mads Ager (chromium), 2014-09-11 06:40:15]

LGTM

[haraken, 2014-09-11 06:56:03]

LGTM!

[tkent, 2014-09-11 07:55:47]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2014-09-11 07:56:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/567453002/1

[commit-bot: I haz the power, 2014-09-11 10:23:29]

Committed patchset #1 (id:1) as 181810