Switch SupportsUserData uses to use unique_ptr.

ios/chrome/browser/ui/dialogs/javascript_dialog_blocking_util.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/chrome/browser/ui/dialogs/javascript_dialog_blocking_util.h"
 
 #import <objc/runtime.h>
 
 #include "base/logging.h"
+#include "base/memory/ptr_util.h"
 #include "ios/web/public/web_state/web_state.h"
 #include "ios/web/public/web_state/web_state_observer.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace {
 // The key under which JavaScriptDialogBlockingStates are associated with
 // their WebStates.
@@ skipping 23 matching lines @@
 
   // The JavaScriptDialogBlockingState owned by this wrapper.
   JavaScriptDialogBlockingState* state() const { return state_.get(); }
   void set_state(JavaScriptDialogBlockingState* state) { state_.reset(state); }
 
  private:
   std::unique_ptr<JavaScriptDialogBlockingState> state_;
 
   // Private constructor associating the newly created object with |web_state|
   // via its SupportsUserData.
   explicit JavaScriptDialogBlockingStateWrapper(web::WebState* web_state)

[sdefresne, 2017/04/28 10:07:05]

Can you change this constructor to not take the web::WebState* and instead call
SetUserData in FromWebState:

  static JavaScriptDialogBlockingStateWrapper* FromWebState(
      web::WebState* web_state) {
    DCHECK(web_state);
    JavaScriptDialogBlockingStateWrapper* wrapper =
        static_cast<JavaScriptDialogBlockingStateWrapper*>(
            web_state->GetUserData(kBlockingStateKey));
    if (!wrapper) {
        wrapper = new JavaScriptDialogBlockingStateWrapper();
        web_state->SetUserData(kBlockingStateKey, base::WrapUnique(wrapper));
    }
    return wrapper;
  }

 private:
  JavaScriptDialogBlockingStateWrapper() = default;

       : state_(nullptr) {
     DCHECK(web_state);
-    web_state->SetUserData(kBlockingStateKey, this);
+    web_state->SetUserData(kBlockingStateKey, base::WrapUnique(this));
   }
 };
 
 #pragma mark - JavaScriptDialogBlockingState
 
 // Wrapper class used to associated JavaScriptDialogBlockingStates with their
 // WebStates.
 class JavaScriptDialogBlockingState : public web::WebStateObserver {
  public:
   // Factory method.  Guaranteed to return a non-null value.
@@ skipping 64 matching lines @@
   DCHECK(web_state);
   return JavaScriptDialogBlockingState::FromWebState(web_state)
       ->ShouldBlockDialogs();
 }
 
 void DialogBlockingOptionSelected(web::WebState* web_state) {
   DCHECK(web_state);
   JavaScriptDialogBlockingState::FromWebState(web_state)->SetShouldBlockDialogs(
       true);
 }