Switch SupportsUserData uses to use unique_ptr.

chrome/browser/ui/cocoa/tab_dialogs_cocoa.mm

Index: chrome/browser/ui/cocoa/tab_dialogs_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/tab_dialogs_cocoa.mm b/chrome/browser/ui/cocoa/tab_dialogs_cocoa.mm
index a66b2ee678c91e88d4eb4e92e9924821a395c60e..e2576ca1a264d33d80a46874aa339530fd6c3535 100644
--- a/chrome/browser/ui/cocoa/tab_dialogs_cocoa.mm
+++ b/chrome/browser/ui/cocoa/tab_dialogs_cocoa.mm
@@ -20,11 +20,11 @@ void TabDialogs::CreateForWebContents(content::WebContents* contents) {
   DCHECK(contents);
 
   if (!FromWebContents(contents)) {
-    TabDialogs* tab_dialogs =
+    std::unique_ptr<TabDialogs> tab_dialogs =
         ui::MaterialDesignController::IsSecondaryUiMaterial()
-            ? new TabDialogsViewsMac(contents)
-            : new TabDialogsCocoa(contents);
-    contents->SetUserData(UserDataKey(), tab_dialogs);
+            ? base::MakeUnique<TabDialogsViewsMac>(contents)
+            : base::MakeUnique<TabDialogsCocoa>(contents);
+    contents->SetUserData(UserDataKey(), std::move(tab_dialogs));
   }
 }