[Offline Pages] Adds UMA for result of attempts to immediately start background loading.

components/offline_pages/background/request_coordinator.h

Index: components/offline_pages/background/request_coordinator.h
diff --git a/components/offline_pages/background/request_coordinator.h b/components/offline_pages/background/request_coordinator.h
index 830d605e57819174e291103bb0f83ca8b3704ba9..5cb9f06d84ad639f5ecd730e8f4efdfd5a9fb040 100644
--- a/components/offline_pages/background/request_coordinator.h
+++ b/components/offline_pages/background/request_coordinator.h
@@ -166,6 +166,17 @@ class RequestCoordinator : public KeyedService,
   }
 
  private:
+  enum class OfflinerImmediateStartStatus {

[Mark P, 2016/10/06 18:54:41]

Please follow the advice here about enum histograms:
https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histo...

[dougarnett, 2016/10/06 23:05:00]

switched to unscoped enum with explicit values

+    STARTED,
+    BUSY,
+    NOT_ACCEPTED,
+    NO_CONNECTION,
+    NO_EFFECTIVE_CONNECTION,

[Mark P, 2016/10/06 18:54:41]

What's the difference between this one and the one above?  This probably
deserved a comment here and in the histograms.xml enum.

[dougarnett, 2016/10/06 23:05:00]

Done.

+    NOT_STARTED_ON_SVELTE,
+    // NOTE: insert new values above this line and update histogram enum too.
+    STATUS_COUNT,
+  };
+
   // Receives the results of a get from the request queue, and turns that into
   // SavePageRequest objects for the caller of GetQueuedRequests.
   void GetQueuedRequestsCallback(
@@ -205,6 +216,8 @@ class RequestCoordinator : public KeyedService,
   // as to other device conditions).
   void StartProcessingIfConnected();
 
+  OfflinerImmediateStartStatus TryImmediateStart();
+
   // Check the request queue, and schedule a task corresponding
   // to the least restrictive type of request in the queue.
   void ScheduleAsNeeded();