Need a more robust WebSQL disk usage computation.

Need a more robust WebSQL disk usage computation.
https://bugs.webkit.org/show_bug.cgi?id=110805.

Reviewed by Geoffrey Garen.

- Changed DatabaseTracker::usageForOrigin() to compute the disk usage
  for a specified origin by fetching database sizes from the file system
  instead of using cached file size values.

- The OriginQuotaManager and OriginUsageRecord are no longer needed.
  Updated build files to reflect this.

- Removed getMaxSizeForDatabase() from DatabaseManager, DatabaseServer,
  and AbstractDatabaseServer since it is only needed in the backend.

- DatabaseTracker::getMaxSizeForDatabase() now calls usageForOrigin()
  to get the disk usage for its computation.

- The performance difference for this changes is a 1.6% degradation
  per additional database whose size needs to be fetched. This is a
  worst case estimated based on the disk-stat-speed-test.html benchmark
  (attached to bugzilla). The benchmark writes an average of 16 bytes per
  transaction. Most real-world transactions will likely write more
  content than that. Since disk write IO time will dominate over memory
  read time for fetching the file size, the degradation ratio will only
  reduce with larger workloads.

No layout test, but there is a quota-test.html attached to bugzilla.
The test is a webpage that can be loaded into multiple tabs to
consuming storage space. While the test is running, we can run a
"du -k; du -k *" on the database directory to verify that the total
disk usage does not far exceed the allowed quota (some small error
is expected). Without this change, each database from each tab may
exceed the quota by that same maginitude of error.

* CMakeLists.txt:
* GNUmakefile.list.am:
* Modules/webdatabase/AbstractDatabaseServer.h:
* Modules/webdatabase/Database.cpp:
* Modules/webdatabase/Database.h:
* Modules/webdatabase/DatabaseBackendBase.cpp:
(WebCore::DatabaseBackendBase::maximumSize):
* Modules/webdatabase/DatabaseManager.cpp:
* Modules/webdatabase/DatabaseManager.h:
* Modules/webdatabase/DatabaseServer.cpp:
* Modules/webdatabase/DatabaseServer.h:
* Modules/webdatabase/DatabaseTracker.cpp:
(WebCore::DatabaseTracker::hasAdequateQuotaForOrigin):
(WebCore::DatabaseTracker::canEstablishDatabase):
(WebCore::DatabaseTracker::retryCanEstablishDatabase):
(WebCore::DatabaseTracker::getMaxSizeForDatabase):
(WebCore::DatabaseTracker::fullPathForDatabaseNoLock):
(WebCore::DatabaseTracker::fullPathForDatabase):
(WebCore::DatabaseTracker::addOpenDatabase):
(WebCore::DatabaseTracker::removeOpenDatabase):
(WebCore::DatabaseTracker::usageForOrigin):
(WebCore::DatabaseTracker::deleteOrigin):
(WebCore::DatabaseTracker::deleteDatabase):
* Modules/webdatabase/DatabaseTracker.h:
* Modules/webdatabase/OriginQuotaManager.cpp: Removed.
* Modules/webdatabase/OriginQuotaManager.h: Removed.
* Modules/webdatabase/OriginUsageRecord.cpp: Removed.
* Modules/webdatabase/OriginUsageRecord.h: Removed.
* Modules/webdatabase/SQLTransactionBackend.cpp:
(WebCore::SQLTransactionBackend::runCurrentStatementAndGetNextState):
* Modules/webdatabase/SQLTransactionBackendSync.cpp:
(WebCore::SQLTransactionBackendSync::executeSQL):
* Modules/webdatabase/SQLTransactionClient.cpp:
* Modules/webdatabase/SQLTransactionClient.h:
* Modules/webdatabase/chromium/SQLTransactionClientChromium.cpp:
* Target.pri:
* WebCore.gyp/WebCore.gyp:
* WebCore.gypi:
* WebCore.vcproj/WebCore.vcproj:
* WebCore.vcxproj/WebCore.vcxproj:
* WebCore.vcxproj/WebCore.vcxproj.filters:
* WebCore.xcodeproj/project.pbxproj:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@144006 268f45cc-cd09-0410-ab3c-d52691b4dbfc