Adds EngineGeolocationFeature for Blimp Geolocation project.

blimp/engine/feature/geolocation/blimp_location_provider.h

Index: blimp/engine/feature/geolocation/blimp_location_provider.h
diff --git a/blimp/engine/feature/geolocation/blimp_location_provider.h b/blimp/engine/feature/geolocation/blimp_location_provider.h
index d3d16f22a9041915f79a05dd2465a446497b9479..a13b74187d4b6a342f94ee1d1663944a3a9a4297 100644
--- a/blimp/engine/feature/geolocation/blimp_location_provider.h
+++ b/blimp/engine/feature/geolocation/blimp_location_provider.h
@@ -5,6 +5,7 @@
 #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 "content/public/browser/location_provider.h"
 #include "content/public/common/geoposition.h"
 
@@ -14,24 +15,41 @@ namespace engine {
 // Location provider for Blimp using the device's provider over the network.
 class BlimpLocationProvider : public content::LocationProvider {
  public:
+  // A delegate that handles outgoing geolocation messages.
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Implments subset of LocationProvider's functions.

[Wez, 2016/07/14 01:19:22]

typo: Implements.

[CJ, 2016/07/14 23:55:09]

Done.

+    virtual void StartProvider(bool enable_high_accuracy) = 0;
+    virtual void StopProvider() = 0;
+    virtual void RequestRefresh() = 0;
+
+    virtual void SetUpdateCallback(
+        const base::Callback<void(const content::Geoposition&)>& callback) = 0;
+  };
+
   BlimpLocationProvider();
   ~BlimpLocationProvider() override;
 
+  void SetDelegate(base::WeakPtr<Delegate> delegate);
+
   // content::LocationProvider implementation.
   bool StartProvider(bool high_accuracy) override;
   void StopProvider() override;
   void GetPosition(content::Geoposition* position) override;
   void RequestRefresh() override;
   void OnPermissionGranted() override;
-
- private:
-  void NotifyCallback(const content::Geoposition& position);
-  void OnLocationResponse(const content::Geoposition& position);
   void SetUpdateCallback(
       const LocationProviderUpdateCallback& callback) override;
 
-  LocationProviderUpdateCallback callback_;
+ private:
+  // This delegate handles a subset of the LocationProvider functionality.
+  // The lifetime of the delegate relative to the BlimpLocationProvider
+  // is unknown.
+  base::WeakPtr<Delegate> delegate_;
 
+  // Needed for GetPosition(), which returns a cached position immediately.
   content::Geoposition position_;
 
   DISALLOW_COPY_AND_ASSIGN(BlimpLocationProvider);