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

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

 // 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.
 
 #ifndef IOS_PUBLIC_PROVIDER_CHROME_BROWSER_SIGNIN_FAKE_CHROME_IDENTITY_SERVICE_H_
 #define IOS_PUBLIC_PROVIDER_CHROME_BROWSER_SIGNIN_FAKE_CHROME_IDENTITY_SERVICE_H_
 
 #include "ios/public/provider/chrome/browser/signin/chrome_identity_service.h"
 
 #include "base/mac/scoped_nsobject.h"
@@ skipping 23 matching lines @@
 
   bool IsValidIdentity(ChromeIdentity* identity) const override;
   ChromeIdentity* GetIdentityWithGaiaID(
       const std::string& gaia_id) const override;
   bool HasIdentities() const override;
   NSArray* GetAllIdentities() const override;
   NSArray* GetAllIdentitiesSortedForDisplay() const override;
   void ForgetIdentity(ChromeIdentity* identity,
                       ForgetIdentityCallback callback) override;
 
-  virtual void GetAccessToken(
-      ChromeIdentity* identity,
-      const std::string& client_id,
-      const std::string& client_secret,
-      const std::set<std::string>& scopes,
-      const ios::AccessTokenCallback& callback) override;
+  virtual void GetAccessToken(ChromeIdentity* identity,
+                              const std::string& client_id,
+                              const std::string& client_secret,
+                              const std::set<std::string>& scopes,
+                              ios::AccessTokenCallback callback) override;
 
   virtual void GetAvatarForIdentity(ChromeIdentity* identity,
                                     GetAvatarCallback callback) override;
 
   virtual UIImage* GetCachedAvatarForIdentity(
       ChromeIdentity* identity) override;
 
   virtual void GetHostedDomainForIdentity(
       ChromeIdentity* identity,
       GetHostedDomainCallback callback) override;
@@ skipping 19 matching lines @@
   // is unknown.
   void RemoveIdentity(ChromeIdentity* identity);
 
  private:
   base::scoped_nsobject<NSMutableArray> identities_;
 };
 
 }  // namespace ios
 
 #endif  // IOS_PUBLIC_PROVIDER_CHROME_BROWSER_SIGNIN_FAKE_CHROME_IDENTITY_SERVICE_H_