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

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

 // Copyright 2015 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_CHROME_IDENTITY_SERVICE_H_
 #define IOS_PUBLIC_PROVIDER_CHROME_BROWSER_SIGNIN_CHROME_IDENTITY_SERVICE_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 139 matching lines @@
   // authentication token.
   // This may be called on an arbitrary thread, but callback will always be on
   // the main thread.
   virtual void ForgetIdentity(ChromeIdentity* identity,
                               ForgetIdentityCallback callback);
 
   // Asynchronously retrieves access tokens for the given identity and scopes.
   // Uses the default client id and client secret.
   virtual void GetAccessToken(ChromeIdentity* identity,
                               const std::set<std::string>& scopes,
-                              const AccessTokenCallback& callback);
+                              AccessTokenCallback callback);
 
   // Asynchronously retrieves access tokens for the given identity and scopes.
   virtual void GetAccessToken(ChromeIdentity* identity,
                               const std::string& client_id,
                               const std::string& client_secret,
                               const std::set<std::string>& scopes,
-                              const AccessTokenCallback& callback);
+                              AccessTokenCallback callback);
 
   // Fetches the profile avatar, from the cache or the network.
   // For high resolution iPads, returns large images (200 x 200) to avoid
   // pixelization. Calls back on the main thread.
   virtual void GetAvatarForIdentity(ChromeIdentity* identity,
                                     GetAvatarCallback callback);
 
   // Synchronously returns any cached avatar, or nil.
   // GetAvatarForIdentity() should be generally used instead of this method.
   virtual UIImage* GetCachedAvatarForIdentity(ChromeIdentity* identity);
@@ skipping 40 matching lines @@
 
  private:
   base::ObserverList<Observer, true> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeIdentityService);
 };
 
 }  // namespace ios
 
 #endif  // IOS_PUBLIC_PROVIDER_CHROME_BROWSER_SIGNIN_CHROME_IDENTITY_SERVICE_H_