Move ExtensionProcessManager to src/extensions, part 3 - remove Browser

Introduce ExtensionHostFactory to hold Browser-specific ExtensionHost
creation.

BUG=313481
TEST=browser_tests, unit_tests

Review URL: https://codereview.chromium.org/57923009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233504 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233504
Tear down IndexedDB dispatcher before WebKit is torn down

Ensure callback objects held by the Indexed DB dispatcher are released
before WebKit and V8 are torn down, since the callback objects hold V8
handles.

This is the same patch as crrev.com/50333004 which landed as r232620
but reverted as r232649 due to timeouts on XP - I just tweaked the
test constants slightly.

BUG=308988
TBR=marja@chromium.org,jamesr@chromium.org,dgrogan@chromium.org

Review URL: https://codereview.chromium.org/58113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233505 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233505