Hooks together Geolocation Feature in the Client and Engine.

blimp/engine/feature/geolocation/engine_geolocation_feature.cc

Index: blimp/engine/feature/geolocation/engine_geolocation_feature.cc
diff --git a/blimp/engine/feature/geolocation/engine_geolocation_feature.cc b/blimp/engine/feature/geolocation/engine_geolocation_feature.cc
index 4cce48905ee5dd38c999ad81fc49f970beb7e981..13eee8ba12e7f2d22bffa1a7d4903710089de0d3 100644
--- a/blimp/engine/feature/geolocation/engine_geolocation_feature.cc
+++ b/blimp/engine/feature/geolocation/engine_geolocation_feature.cc
@@ -9,6 +9,7 @@
 
 #include "base/memory/ptr_util.h"
 #include "base/memory/weak_ptr.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "blimp/common/create_blimp_message.h"
 #include "blimp/common/proto/blimp_message.pb.h"
 #include "blimp/common/proto/geolocation.pb.h"
@@ -20,6 +21,7 @@
 namespace blimp {
 namespace engine {
 namespace {
+
 class BlimpGeolocationDelegate : public device::GeolocationDelegate {
  public:
   explicit BlimpGeolocationDelegate(
@@ -120,7 +122,8 @@ void EngineGeolocationFeature::ProcessMessage(
 
 void EngineGeolocationFeature::NotifyCallback(
     const device::Geoposition& position) {
-  geoposition_received_callback_.Run(position);
+  task_runner_->PostTask(FROM_HERE,
+                         base::Bind(geoposition_received_callback_, position));
 }
 
 void EngineGeolocationFeature::RequestAccuracy(
@@ -151,6 +154,12 @@ void EngineGeolocationFeature::OnPermissionGranted() {
 void EngineGeolocationFeature::SetUpdateCallback(
     const GeopositionReceivedCallback& callback) {
   geoposition_received_callback_ = callback;
+  SetTaskRunner(base::ThreadTaskRunnerHandle::Get());
+}
+
+void EngineGeolocationFeature::SetTaskRunner(
+    scoped_refptr<base::SingleThreadTaskRunner> runner) {
+  task_runner_ = std::move(runner);

[Wez, 2016/09/01 02:45:43]

Why can't we just assign task_runner_ directly in SetUpdateCallback?

[CJ, 2016/09/01 18:17:05]

It's because ThreadTaskRunnerHandle::Get() returns a const task runner, and cant
be assigned to the non-const |task_runner_|. Is there a better way to handle
this?

[Wez, 2016/09/01 20:08:17]

You can just assigned the result of Get() directly into a
scoped_refptr<TaskRunner> - that's effectively what you're doing by passing it
to SetTaskRunner(), since that takes a scoped_refptr<>.

 }
 
 }  // namespace engine