Refactor Passwords UI so it can be reused by Android.

This CL refactors PasswordManagerHandler into PasswordManagerPresenter
and PasswordUIView. PasswordManagerPresenter has the common password logic
to manipulate PasswordStore and update a PasswordUIView. PasswordUIView is
an interface that UI views need to implement for displaying passwords.
The WebUI code in PasswordManagerHandler is now moved to a new class
PasswordWebUIView which implements PasswordUIView.

Android will implement its own PasswordUIView that will be used to display
password lists using Android UI.

BUG=248589
TEST=Manual
R=dubroy@chromium.org, jhawkins@chromium.org

Review URL: https://codereview.chromium.org/39253002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234576 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234576