Reuse one UserPolicySigninService for Android and iOS.

chrome/browser/policy/cloud/DEPS

 # The //chrome/browser/policy code is being converted into a component at
 # //components/policy. This DEPS file is temporarily restricting the include
 # rules for this code; once all the exceptions are fixed then the code will
 # be moved, and this file will be removed.
 # http://crbug.com/271392
 
 include_rules = [
   "-chrome",
   "-chromeos",
   "-content",
   "+chrome/browser/policy",
   "+chrome/browser/policy/cloud",
 ]
 
 specific_include_rules = {
   # These files will stay.
   r"(cloud_policy_browsertest|"
   r"cloud_policy_manager_browsertest|"
   r"component_cloud_policy_browsertest|"
   r"device_management_service_browsertest|"
   r"test_request_interceptor|"
   r"policy_header_service_factory|"
   r"policy_header_service_unittest|"
   r"user_cloud_policy_invalidator|"
   r"user_cloud_policy_invalidator_factory|"
   r"user_cloud_policy_manager_factory|"
-  r"user_policy_signin_service_android|"
   r"user_policy_signin_service_base|"
   r"user_policy_signin_service|"
   r"user_policy_signin_service_factory|"
-  r"user_policy_signin_service_ios|"
+  r"user_policy_signin_service_mobile|"
   r"user_policy_signin_service_unittest)"
   r"\.(cc|h|mm)": [
     "+chrome",
     "+chromeos",
     "+content/public/browser",
     "+content/public/common",
     "+content/public/test",
     "+content/test/net",
   ],
 
   r"cloud_policy_browsertest.cc": [
     "+sync/internal_api/public/base/invalidation.h",
   ],
 
   r"cloud_policy_invalidator.h": [
     "+sync/internal_api/public/base/invalidation.h",
   ],
 
   # TODO(joaodasilva): remove these exceptions.
   r"cloud_policy_invalidator\.cc": [
     "+chrome/browser/invalidation/invalidation_service.h",
   ],
 
   r"cloud_policy_invalidator_unittest\.cc": [
     "+chrome/browser/invalidation/fake_invalidation_service.h",
   ],
 }