Move PrefMember and PrefChangeRegistrar to api directory.

chrome/browser/api/DEPS

 # The chrome/browser/api directory is for programming interfaces
 # provided by Chrome to Browser Components that run within Chrome.
 # Files here are not allowed to include stuff under chrome/browser
 # since that would leak implementation details to users of the APIs.
 #
 # APIs can be either pure-virtual to allow specialization at runtime,
 # or they can be non-virtual and specialized per platform (or
 # otherwise at compile time), or a mix of non-virtual and virtual.
 # The primary initial objective is to break Browser Components'
 # dependencies on implementation details, so non-virtual classes in
 # header files that do not expose any headers from chrome/browser
 # except for chrome/browser/api are acceptable.
 #
 # Note that for non-virtual APIs, there is an increased risk of an
 # implicit link-time dependency remaining from the user of the API to
 # the implementation.  We are accepting this risk initially, but plan
 # to write a new type of link-time or target-level set of dependency
 # rules to help us find such problems and reduce them over time.
 #
 # The directory structure under chrome/browser/api/ is a mirror of
 # those parts of the chrome/browser/ structure that APIs have been
 # extracted from.  Hence, an API defined in chrome/browser/api/x/y/z
 # is likely to be implemented in a directory chrome/browser/x/y/z.
 #
 # See http://www.chromium.org/developers/design-documents/browser-components
 include_rules = [
   "-chrome/browser",
   "+chrome/browser/api",
 ]
+
+specific_include_rules = {
+  ".*_[a-z]+test\.cc": [
+    "+chrome/test",
+  ],
+}