Remove the dependency of PasswordStore on BrowserContextKeyedService

This CL splits PasswordStore into a wrapper, PasswordStoreService, and the core class (PasswordStore).
The wrapper's only purpose is to represent the BCKS for PasswordStore.
The core class will be moved into /components.

BUG=335155,335154

Review URL: https://codereview.chromium.org/149393011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249034 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249034
aw: Fix some style issues in tests

NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/155943002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249035 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249035