[DIAL] Break circular dependency in DialFetchDeviceDescriptionFunction.

chrome/browser/extensions/api/dial/dial_api.cc

Index: chrome/browser/extensions/api/dial/dial_api.cc
diff --git a/chrome/browser/extensions/api/dial/dial_api.cc b/chrome/browser/extensions/api/dial/dial_api.cc
index 6099c0277d891a24400da675b77269a342d7dfe3..a055355a0c0bacd798c0d00c705b75be80eabab2 100644
--- a/chrome/browser/extensions/api/dial/dial_api.cc
+++ b/chrome/browser/extensions/api/dial/dial_api.cc
@@ -240,6 +240,7 @@ void DialFetchDeviceDescriptionFunction::MaybeStartFetch(const GURL& url) {
 
 void DialFetchDeviceDescriptionFunction::OnFetchComplete(

[mark a. foltz, 2017/02/02 20:27:32]

Can you add a comment in device_description_fetcher.h indicating that it should
be destroyed in the onsuccess/onerror callbacks?

[imcheng, 2017/02/02 20:44:31]

I added comment here explaining why we have to destroy it here. It's due to the
way we bind the callbacks passed in.

     const api::dial::DialDeviceDescriptionData& result) {
+  device_description_fetcher_.reset();

[mark a. foltz, 2017/02/02 20:27:32]

Would resetting the non-invoked callback in DeviceDescriptionFetcher also fix
the problem by dropping the additional reference?  That wouldn't require the
client to drop references explicitly.

[imcheng, 2017/02/02 20:44:31]

Yes, that would work too. But I see no reason to hold on to the fetcher since
it's no longer (re)usable.

   api::dial::DialDeviceDescription device_description;
   device_description.device_label = params_->device_label;
   device_description.app_url = result.app_url.spec();
@@ -250,6 +251,7 @@ void DialFetchDeviceDescriptionFunction::OnFetchComplete(
 
 void DialFetchDeviceDescriptionFunction::OnFetchError(
     const std::string& message) {
+  device_description_fetcher_.reset();
   SetError(message);
   SendResponse(false);
 }