Makes use of EngineGeolocationFeature weak_ptr threadsafe.

blimp/engine/feature/geolocation/blimp_location_provider.h

 // Copyright (c) 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.
 
 #ifndef BLIMP_ENGINE_FEATURE_GEOLOCATION_BLIMP_LOCATION_PROVIDER_H_
 #define BLIMP_ENGINE_FEATURE_GEOLOCATION_BLIMP_LOCATION_PROVIDER_H_
 
 #include "base/memory/weak_ptr.h"
 #include "blimp/common/proto/geolocation.pb.h"
 #include "device/geolocation/geoposition.h"
 #include "device/geolocation/location_provider.h"
 
 namespace blimp {
 namespace engine {
 
 // Location provider for Blimp using the device's provider over the network.
 class BlimpLocationProvider : public device::LocationProvider {
  public:
   // A delegate that implements a subset of LocationProvider's functions.
+  // All methods will be executed on |delegate_task_runner_|.
   class Delegate {
    public:
     using GeopositionReceivedCallback =
         base::Callback<void(const device::Geoposition&)>;
-
     virtual ~Delegate() {}
 
     virtual void RequestAccuracy(
         GeolocationSetInterestLevelMessage::Level level) = 0;
     virtual void OnPermissionGranted() = 0;
     virtual void SetUpdateCallback(
         const GeopositionReceivedCallback& callback) = 0;
   };
 
-  explicit BlimpLocationProvider(base::WeakPtr<Delegate> delegate);
+  BlimpLocationProvider(
+      base::WeakPtr<Delegate> delegate,
+      scoped_refptr<base::SequencedTaskRunner> delegate_task_runner);
   ~BlimpLocationProvider() override;
 
   // device::LocationProvider implementation.
   bool StartProvider(bool high_accuracy) override;
   void StopProvider() override;
   const device::Geoposition& GetPosition() override;
   void OnPermissionGranted() override;
   void SetUpdateCallback(
       const LocationProviderUpdateCallback& callback) override;
 
+  void OnLocationUpdate(const device::Geoposition& geoposition);

[Wez, 2016/10/07 21:42:46]

This should be private, since it's an internal implementation detail of
BlimpLocationProvider.

Since you need to Bind() to it from the InvokeGeolocationCallback() function you
may need to move that function to be a static member, so it has visibility into
the private bit of the class.

[CJ, 2016/10/08 00:05:55]

Done.

+
  private:
   // This delegate handles a subset of the LocationProvider functionality.
   base::WeakPtr<Delegate> delegate_;
 
+  scoped_refptr<base::SequencedTaskRunner> delegate_task_runner_;
   device::Geoposition cached_position_;
 
   // True if a successful StartProvider call has occured.
   bool is_started_;
 
+  LocationProviderUpdateCallback location_update_callback_;
+
+  base::WeakPtrFactory<BlimpLocationProvider> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(BlimpLocationProvider);
 };
 
 }  // namespace engine
 }  // namespace blimp
 
 #endif  // BLIMP_ENGINE_FEATURE_GEOLOCATION_BLIMP_LOCATION_PROVIDER_H_