Create and integrate a metrics service client into Blimp engine.

blimp/engine/common/blimp_browser_context.cc

Index: blimp/engine/common/blimp_browser_context.cc
diff --git a/blimp/engine/common/blimp_browser_context.cc b/blimp/engine/common/blimp_browser_context.cc
index 6a2a7ec04ad9ba83d257b766bf9ef850515804b0..69c0a1f00dc07eb62956011ebe6054e1fe9c2581 100644
--- a/blimp/engine/common/blimp_browser_context.cc
+++ b/blimp/engine/common/blimp_browser_context.cc
@@ -7,14 +7,26 @@
 #include "base/bind.h"
 #include "base/environment.h"
 #include "base/files/file_util.h"
+#include "base/memory/ptr_util.h"
 #include "base/nix/xdg_util.h"
 #include "base/path_service.h"
 #include "blimp/engine/app/blimp_permission_manager.h"
+#include "components/metrics/metrics_service.h"
+#include "components/pref_registry/pref_registry_syncable.h"
+#include "components/prefs/in_memory_pref_store.h"
+#include "components/prefs/pref_service.h"
+#include "components/prefs/pref_service_factory.h"
 #include "content/public/browser/background_sync_controller.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/common/content_switches.h"
 
+namespace {
+// Shows notifications which correspond to PersistentPrefStore's reading errors.

[Wez, 2016/04/26 01:38:19]

Looks like the body of this function is missing?  Is it supposed to be declared
in-line?

[Jess, 2016/04/26 21:24:11]

PTAL at the new comment.

+void HandleReadError(PersistentPrefStore::PrefReadError error) {
+}
+}  // namespace
+
 namespace blimp {
 namespace engine {
 
@@ -68,6 +80,17 @@ BlimpBrowserContext::~BlimpBrowserContext() {
   }
 }
 
+void BlimpBrowserContext::Initialize() {
+  InitPrefService();
+  BlimpMetricsServiceClient::GetInstance()->Initialize(
+      pref_service_.get(),
+      GetSystemRequestContextGetter());
+}
+
+void BlimpBrowserContext::Finalize() {
+  BlimpMetricsServiceClient::GetInstance()->Finalize();
+}
+
 void BlimpBrowserContext::InitWhileIOAllowed() {
   // Ensures ~/.config/blimp_engine directory exists.
   std::unique_ptr<base::Environment> env(base::Environment::Create());
@@ -79,6 +102,17 @@ void BlimpBrowserContext::InitWhileIOAllowed() {
   BrowserContext::Initialize(this, path_);
 }
 
+void BlimpBrowserContext::InitPrefService() {

[Wez, 2016/04/26 01:38:19]

If I understand this code correctly (big "if") this is doing three things:

1. Creating a PrefRegistry & registering the metrics service preferences with
it.

2. Creating an in-memory preferences store, to hold metrics logs

3. Attaching it to that registry.

It would therefore be helpful to break this code up into logical blocks with
blob-level comments, i.e. something like:

  // Create a PrefRegistry and populate it with MetricsService prefs.
  ...

  // Create an in-memory PrefStore.
  ...

  // Create a PrefService binding the metrics PrefRegistry to our in-memory
store.
  ...

nit: It's also really unfortunate that those interfaces use bare pointers when
many of the objects being passed-around are ref-counted, but I don't think
there's much we can do about that in this CL, except perhaps mentioning in that
third comment that the PrefService ends up owning the PrefRegistry and store.
;-(

[Jess, 2016/04/26 21:24:11]

Done.

+  scoped_refptr<user_prefs::PrefRegistrySyncable> pref_registry(
+      new user_prefs::PrefRegistrySyncable());
+  metrics::MetricsService::RegisterPrefs(pref_registry.get());
+  PrefServiceFactory pref_service_factory;
+  // The pref storage for metrics logs.
+  pref_service_factory.set_user_prefs(new InMemoryPrefStore());
+  pref_service_factory.set_read_error_callback(base::Bind(&HandleReadError));
+  pref_service_ = pref_service_factory.Create(pref_registry.get());
+}
+
 std::unique_ptr<content::ZoomLevelDelegate>
 BlimpBrowserContext::CreateZoomLevelDelegate(const base::FilePath&) {
   return nullptr;