[iOS] Replacing WeakNSProtocol by __weak

Change-Id: I071ed925c3f6b9764381b282b108c7f7eb79a407
Reviewed-on: https://chromium-review.googlesource.com/1203552Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588842}

components/signin/ios/browser/BUILD.gn

@@ -22,7 +22,6 @@ source_set("browser") {
 
   deps = [
     ":active_state_manager",
-    "//base",
     "//components/content_settings/core/browser",
     "//components/google/core/browser",
     "//components/keyed_service/core",

components/signin/ios/browser/oauth2_token_service_observer_bridge.h

@@ -7,7 +7,6 @@
 
 #import <Foundation/Foundation.h>
 
-#import "base/ios/weak_nsobject.h"
 #include "base/macros.h"
 #include "google_apis/gaia/oauth2_token_service.h"
 
@@ -50,7 +49,7 @@ class OAuth2TokenServiceObserverBridge : public OAuth2TokenService::Observer {
 
  private:
   OAuth2TokenService* token_service_;  // weak
-  base::WeakNSProtocol<id<OAuth2TokenServiceObserverBridgeDelegate>> delegate_;
+  __weak id<OAuth2TokenServiceObserverBridgeDelegate> delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(OAuth2TokenServiceObserverBridge);
 };