Store unique_ptr instead of raw poiter in extension callback map

There is callback map in extension function dispatcher, which store
pointers on callback wrappers. But it force to remember to delete
wrapper after erase from map. This may lead to memory leak.
To prevent it, raw pointer in map was replaced by unique_ptr (like in
other callback map in same class).

BUG=None
R=finnur

Review-Url: https://codereview.chromium.org/2850533002
Cr-Commit-Position: refs/heads/master@{#467932}

extensions/browser/extension_function_dispatcher.cc

@@ -140,8 +140,6 @@ class ExtensionFunctionDispatcher::UIThreadResponseCallbackWrapper
       dispatcher_->ui_thread_response_callback_wrappers_
           .erase(render_frame_host);
     }
-
-    delete this;
   }
 
   ExtensionFunction::ResponseCallback CreateCallback(int request_id) {
@@ -370,9 +368,9 @@ void ExtensionFunctionDispatcher::Dispatch(
       callback_wrapper =
           new UIThreadResponseCallbackWrapper(AsWeakPtr(), render_frame_host);
       ui_thread_response_callback_wrappers_[render_frame_host] =
-          callback_wrapper;
+          base::WrapUnique(callback_wrapper);
     } else {
-      callback_wrapper = iter->second;
+      callback_wrapper = iter->second.get();
     }
     DispatchWithCallbackInternal(
         params, render_frame_host, render_process_id,

extensions/browser/extension_function_dispatcher.h

@@ -169,7 +169,8 @@ class ExtensionFunctionDispatcher
   // This map doesn't own either the keys or the values. When a RenderFrameHost
   // instance goes away, the corresponding entry in this map (if exists) will be
   // removed.
-  typedef std::map<content::RenderFrameHost*, UIThreadResponseCallbackWrapper*>
+  typedef std::map<content::RenderFrameHost*,
+                   std::unique_ptr<UIThreadResponseCallbackWrapper>>
       UIThreadResponseCallbackWrapperMap;
   UIThreadResponseCallbackWrapperMap ui_thread_response_callback_wrappers_;