Allow tests to provide a TestingFactoryFunction for NULLWhileTesting factories.
TestingProfile provides a means by which tests may provide
TestingFactoryFunctions. Previously, these were discaded by
BrowserContextDependencyManager::DoCreateBrowserContextServices if
ServiceIsNULLWhileTesting returned true. This made it impossible for
tests to provide factory functions that were in place at the very
beginning of the profile lifecycle since DoCreateBrowserContextServices
would NULL them out. With this change, DoCreateBrowserContextServices
will not override test-provided factory functions.
R=erg@chromium.org
BUG=
Review URL: https://codereview.chromium.org/
354653004
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@279691 0039d316-1c4b-4281-b951-d872f2087c98