Change GetAccessToken APIs so that they don't pass const ref to blocks.

ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/mac/scoped_block.h"
 #include "base/strings/sys_string_conversions.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #import "ios/public/provider/chrome/browser/signin/fake_chrome_identity.h"
 #import "ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.h"
 #include "ios/public/provider/chrome/browser/signin/signin_resources_provider.h"
 
 using ::testing::_;
 using ::testing::Invoke;
 
 namespace {
 
 void FakeGetAccessToken(ChromeIdentity*,
                         const std::string&,
                         const std::string&,
                         const std::set<std::string>&,
-                        const ios::AccessTokenCallback& callback) {
+                        ios::AccessTokenCallback callback) {
   base::mac::ScopedBlock<ios::AccessTokenCallback> safe_callback(
       [callback copy]);
 
   // |GetAccessToken| is normally an asynchronous operation (that requires some
   // network calls), this is replicated here by dispatching it.
   dispatch_async(dispatch_get_main_queue(), ^{
     // Token and expiration date. It should be larger than typical test
     // execution because tests usually setup mock to expect one token request
     // and then rely on access token being served from cache.
     NSTimeInterval expiration = 60.0;
@@ skipping 171 matching lines @@
       callback(nil);
     });
   }
 }
 
 void FakeChromeIdentityService::GetAccessToken(
     ChromeIdentity* identity,
     const std::string& client_id,
     const std::string& client_secret,
     const std::set<std::string>& scopes,
-    const ios::AccessTokenCallback& callback) {
+    ios::AccessTokenCallback callback) {
   FakeGetAccessToken(identity, client_id, client_secret, scopes, callback);
 }
 
 UIImage* FakeChromeIdentityService::GetCachedAvatarForIdentity(
     ChromeIdentity* identity) {
   return FakeGetCachedAvatarForIdentity(identity);
 }
 
 void FakeChromeIdentityService::GetAvatarForIdentity(
     ChromeIdentity* identity,
@@ skipping 25 matching lines @@
 }
 
 void FakeChromeIdentityService::RemoveIdentity(ChromeIdentity* identity) {
   if ([identities_ indexOfObject:identity] != NSNotFound) {
     [identities_ removeObject:identity];
     FireIdentityListChanged();
   }
 }
 
 }  // namespace ios