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..418b10b4da9971b6ac9c5e69288869ace68f99a5 100644
--- a/blimp/engine/feature/geolocation/blimp_location_provider.h
+++ b/blimp/engine/feature/geolocation/blimp_location_provider.h
@@ -14,6 +14,23 @@ namespace engine {
 // Location provider for Blimp using the device's provider over the network.
 class BlimpLocationProvider : public content::LocationProvider {
  public:
+  // A delegate that handles geolocation related outcoming and incoming events.
+  class BlimpLocationProviderDelegate {

[Kevin M, 2016/06/29 17:52:55]

nit: Just "Delegate" should suffice

[CJ, 2016/07/11 23:21:06]

Done.

+   public:
+    virtual ~BlimpLocationProviderDelegate() {};
+
+    // Notifies the client that the is listening engine is listening for
+    // geoposition information with the given accuracy.
+    virtual void SendUpdateListenStateMessage(bool enable_high_accuracy) = 0;

[Kevin M, 2016/06/29 17:52:55]

Remove "Send" and "Message" from these method names. The message sending aspect
shouldn't be exposed to this layer.

[CJ, 2016/07/11 23:21:07]

Done.

+
+    // Notifies the client that the engine is no longer listening for
+    // updates.
+    virtual void SendStopListenStateMessage() = 0;

[Kevin M, 2016/06/29 17:52:55]

I thought we were just going to have Update, not Start/Stop (or Update/Stop in
this case)?

[CJ, 2016/07/11 23:21:06]

It is expressed that way in the proto, but I thought it would make sense just to
have separate functions. 

+
+    // Requests an updated geoposition from the client.
+    virtual void SendRequestRefreshMessage() = 0;
+  };
+
   BlimpLocationProvider();
   ~BlimpLocationProvider() override;
 
@@ -23,10 +40,13 @@ class BlimpLocationProvider : public content::LocationProvider {
   void GetPosition(content::Geoposition* position) override;
   void RequestRefresh() override;
   void OnPermissionGranted() override;
+  void OnLocationResponse(const content::Geoposition& position);
+  void SetDelegate(BlimpLocationProviderDelegate* delegate);

[Kevin M, 2016/06/29 17:52:55]

These methods should be placed above the "implementation" block

[CJ, 2016/07/11 23:21:06]

Done.

 
  private:
+  BlimpLocationProviderDelegate* delegate_ = nullptr;
+
   void NotifyCallback(const content::Geoposition& position);
-  void OnLocationResponse(const content::Geoposition& position);
   void SetUpdateCallback(
       const LocationProviderUpdateCallback& callback) override;