Convert //ios from scoped_ptr to std::unique_ptr.

ios/web/interstitials/native_web_interstitial_impl.mm

Index: ios/web/interstitials/native_web_interstitial_impl.mm
diff --git a/ios/web/interstitials/native_web_interstitial_impl.mm b/ios/web/interstitials/native_web_interstitial_impl.mm
index 438705e22e9a328817b90d94b577654bcaf1b2fc..a2a86dd7cc7a6ab5e153232157983295b05eb6a4 100644
--- a/ios/web/interstitials/native_web_interstitial_impl.mm
+++ b/ios/web/interstitials/native_web_interstitial_impl.mm
@@ -19,7 +19,7 @@ WebInterstitial* WebInterstitial::CreateNativeInterstitial(
     WebState* web_state,
     bool new_navigation,
     const GURL& url,
-    scoped_ptr<NativeWebInterstitialDelegate> delegate) {
+    std::unique_ptr<NativeWebInterstitialDelegate> delegate) {
   WebStateImpl* web_state_impl = static_cast<WebStateImpl*>(web_state);
   return new NativeWebInterstitialImpl(web_state_impl, new_navigation, url,
                                        std::move(delegate));
@@ -29,7 +29,7 @@ NativeWebInterstitialImpl::NativeWebInterstitialImpl(
     WebStateImpl* web_state,
     bool new_navigation,
     const GURL& url,
-    scoped_ptr<NativeWebInterstitialDelegate> delegate)
+    std::unique_ptr<NativeWebInterstitialDelegate> delegate)
     : web::WebInterstitialImpl(web_state, new_navigation, url),
       delegate_(std::move(delegate)) {
   DCHECK(delegate_);