Creating a helper class for reversing timing functions.

DEPENDS=https://codereview.chromium.org/60323005/ - Adding operator== to TimingFunctionTestHelper.

Review URL: https://codereview.chromium.org/51943004

git-svn-id: svn://svn.chromium.org/blink/trunk@161686 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Prepare for deprecating DatabaseObserver.{h,cc} pt.2

- Change webdatabase code to use blink::Platform::current()->databaseObserver() when it's non-null rather than DatabaseObserver's static methods (so that when embedder implements the new observer code it automatically switches to the new impl)
- Minor fixes in WebPlatformDatabaseObserver, which were found while implementing chrome side code

FIXME: part will be cleaned up later.

BUG=none

Review URL: https://codereview.chromium.org/59423003

git-svn-id: svn://svn.chromium.org/blink/trunk@161687 bbb929c8-8fbe-4397-9dbb-9b2b20218538