Basic UkmService implementation

components/metrics/metrics_service_client.h

Index: components/metrics/metrics_service_client.h
diff --git a/components/metrics/metrics_service_client.h b/components/metrics/metrics_service_client.h
index 6a067afe6b89a79207daf65ca3ea6d5cad013c41..0ef5ff3d038bb1ba51d55646703aad8f9c6fd8a9 100644
--- a/components/metrics/metrics_service_client.h
+++ b/components/metrics/metrics_service_client.h
@@ -20,6 +20,10 @@ namespace base {
 class FilePath;
 }
 
+namespace ukm {
+class UkmService;
+}
+
 namespace metrics {
 
 class MetricsLogUploader;
@@ -37,6 +41,9 @@ class MetricsServiceClient {
   // implementation will own the MetricsService instance being returned).
   virtual MetricsService* GetMetricsService() = 0;
 
+  // Returns the UkmService instance that this client is associated with.
+  virtual ukm::UkmService* GetUkmService() = 0;

[Alexei Svitkine (slow), 2017/01/06 16:34:32]

There's a bunch of other implementations of MetricsServiceClient - e.g. cast, aw
(android webview), blimp (maybe going away?), ios.

Probably we're OK with most of those not having one (except for iOS). If so,
please document that it's valid for this to be null.

Also, maybe provide a default implementation that returns null so that you don't
have to change all those subclasses?

But you *should* change the iOS one, though!

[Steven Holte, 2017/01/06 20:21:26]

Made the default null, added null checks in metrics_service_manager, and added
iOS implementation.

+
   // Registers the client id with other services (e.g. crash reporting), called
   // when metrics recording gets enabled.
   virtual void SetMetricsClientId(const std::string& client_id) = 0;
@@ -85,6 +92,8 @@ class MetricsServiceClient {
   // Creates a MetricsLogUploader with the specified parameters (see comments on
   // MetricsLogUploader for details).
   virtual std::unique_ptr<MetricsLogUploader> CreateUploader(
+      const std::string& server_url,
+      const std::string& mime_type,
       const base::Callback<void(int)>& on_upload_complete) = 0;
 
   // Returns the standard interval between upload attempts.