Create and integrate a metrics service client into Blimp engine.

blimp/engine/session/blimp_engine_session.cc

Index: blimp/engine/session/blimp_engine_session.cc
diff --git a/blimp/engine/session/blimp_engine_session.cc b/blimp/engine/session/blimp_engine_session.cc
index 06f1faf1c4d105fb3b0a0b55079377acebb2e769..138aa916b872810b1394ab5729b74b723cce2731 100644
--- a/blimp/engine/session/blimp_engine_session.cc
+++ b/blimp/engine/session/blimp_engine_session.cc
@@ -217,9 +217,14 @@ BlimpEngineSession::BlimpEngineSession(
                                      gfx::Size(kDefaultDisplayWidth,
                                                kDefaultDisplayHeight));
   render_widget_feature_.SetDelegate(kDummyTabId, this);
+
+  // Initializes the PrefService and MetricsServiceClient for Blimp.
+  browser_context_->Initialize();
 }
 
 BlimpEngineSession::~BlimpEngineSession() {
+  browser_context_->Finalize();
+
   render_widget_feature_.RemoveDelegate(kDummyTabId);
 
   window_tree_host_->GetInputMethod()->RemoveObserver(this);