MediaPerceptionPrivate API impl and testing.

chromeos/dbus/fake_upstart_client.h

Index: chromeos/dbus/fake_upstart_client.h
diff --git a/chromeos/dbus/fake_upstart_client.h b/chromeos/dbus/fake_upstart_client.h
index efcb5e6a6c1344b3e19a417dd0bd3e667b7c182e..64bad371211694dc0ae5bf6b232ee26e9a288e1b 100644
--- a/chromeos/dbus/fake_upstart_client.h
+++ b/chromeos/dbus/fake_upstart_client.h
@@ -25,7 +25,16 @@ class CHROMEOS_EXPORT FakeUpstartClient : public UpstartClient {
   void StartMediaAnalytics(const UpstartCallback& callback) override;
   void StopMediaAnalytics() override;
 
+  void SetStartMediaAnalyticsWillSucceed(bool will_succeed);
+  void SetStartMediaAnalyticsWillStall(bool will_stall);
+
  private:
+  // Sets whether the StartMediaAnalytics method will succeed.
+  bool start_media_analytics_will_succeed_;

[tbarzic, 2017/05/18 19:28:01]

So, I'd do this differently (my main concern is that we don';t really want to
test start-up stalling - we want the request to be eventually handled) :)

I'd change StartMediaAnalytics() to enqueue "start requests",
and provide a hook for a test to verify the request was received, and to run
response:
(though, instead of adding this to FakeUpstartClient, I'd consider creating a
test FakeUpstartClient override specific to your tests - if you bake this here,
you'll probably want to guard this behavior behind a bool variable)

i.e.

std::queue<UpstartCallback> pending_upstart_requests_;

void FakeUpstartClient::StartMediaAnalyticsClient(callback) {
  peding_upstart_requets_.push(callback);
}

bool FakeUpstartClient::HandleNextUpstart(bool succeed) {
  if (pending_upstart_requests_.empty())
    return false;

  UpstartCallback callback = pending_upstart_requests_.front();
  pending_upstart_requests_.pop();

  if (!succeed) {
    callback.Run(succeed);
    return true;
  }

  //default StartMediaAnalytics(callback); 
}

[Luke Sorenson, 2017/05/18 21:24:16]

Done.

+
+  // Sets whether the StartMediaAnalytics method will stall.
+  bool start_media_analytics_will_stall_;
+
   DISALLOW_COPY_AND_ASSIGN(FakeUpstartClient);
 };