Switch MediaSession UMAs to use kMaxValue enumerator value.

clang automatically checks this value is correctly set, and it
simplifies macro usage.

Bug: 742517
Change-Id: I3b53752a7ac00e33167b9fb42fb3801ef8e7d378
Reviewed-on: https://chromium-review.googlesource.com/c/1308082Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605030}

content/browser/media/session/media_session_impl.cc

@@ -80,7 +80,7 @@ MediaSessionUserAction MediaSessionActionToUserAction(
       return MediaSessionUserAction::SeekForward;
   }
   NOTREACHED();
-  return MediaSessionUserAction::Count;
+  return MediaSessionUserAction::Play;
 }
 
 // If the string is not empty then push it to the back of a vector.

content/browser/media/session/media_session_uma_helper.cc

@@ -23,17 +23,12 @@ MediaSessionUmaHelper::~MediaSessionUmaHelper()
 // static
 void MediaSessionUmaHelper::RecordMediaSessionUserAction(
     MediaSessionUserAction action) {
-  UMA_HISTOGRAM_ENUMERATION(
-      "Media.Session.UserAction", static_cast<HistogramBase::Sample>(action),
-      static_cast<HistogramBase::Sample>(MediaSessionUserAction::Count));
+  UMA_HISTOGRAM_ENUMERATION("Media.Session.UserAction", action);
 }
 
 void MediaSessionUmaHelper::RecordSessionSuspended(
     MediaSessionSuspendedSource source) const {
-  UMA_HISTOGRAM_ENUMERATION(
-      "Media.Session.Suspended",
-      static_cast<HistogramBase::Sample>(source),
-      static_cast<HistogramBase::Sample>(MediaSessionSuspendedSource::Count));
+  UMA_HISTOGRAM_ENUMERATION("Media.Session.Suspended", source);
 }
 
 void MediaSessionUmaHelper::RecordRequestAudioFocusResult(bool result) const {

content/browser/media/session/media_session_uma_helper.h

@@ -26,7 +26,7 @@ class CONTENT_EXPORT MediaSessionUmaHelper {
     UI = 2,
     CONTENT = 3,
     SystemTransientDuck = 4,
-    Count // Leave at the end.
+    kMaxValue = SystemTransientDuck,
   };
 
   // Extended enum to blink::mojom::MediaSessionAction, distinguishing default
@@ -41,7 +41,7 @@ class CONTENT_EXPORT MediaSessionUmaHelper {
     NextTrack = 6,
     SeekBackward = 7,
     SeekForward = 8,
-    Count  // Leave at the end.
+    kMaxValue = SeekForward,
   };
 
   MediaSessionUmaHelper();