Let PasswordFormManagerTest have an instance of the TestPasswordManager as a member
Replace the repeated local creation of the same class over again.
Also provide a non-null PasswordManager to every PasswordFormManager. This will be important in the coming CLs where calling SimulateMatchingPhase on a PasswordFormManager will be replaced with calling OnGetPasswordStoreResults, which dereferences the passed PasswordManager.
BUG=520831
Review URL: https://codereview.chromium.org/
1296823002
Cr-Commit-Position: refs/heads/master@{#343671}