Add a histogram for video decoder fallback.

BUG=447732
TEST=Manually inspect chrome:histograms.

Review URL: https://codereview.chromium.org/847223002

Cr-Commit-Position: refs/heads/master@{#311525}

content/browser/media/media_internals.cc

@@ -200,6 +200,7 @@ class MediaInternals::MediaInternalsUMAHandler : public NotificationObserver {
     bool has_audio;
     bool has_video;
     bool video_dds;
+    bool video_decoder_changed;
     std::string audio_codec_name;
     std::string video_codec_name;
     std::string video_decoder;
@@ -207,7 +208,8 @@ class MediaInternals::MediaInternalsUMAHandler : public NotificationObserver {
         : last_pipeline_status(media::PIPELINE_OK),
           has_audio(false),
           has_video(false),
-          video_dds(false) {}
+          video_dds(false),
+          video_decoder_changed(false) {}
   };
 
   // Helper function to report PipelineStatus associated with a player to UMA.
@@ -260,10 +262,6 @@ void MediaInternals::MediaInternalsUMAHandler::SavePlayerState(
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   PlayerInfoMap& player_info = renderer_info_[render_process_id];
   switch (event.type) {
-    case media::MediaLogEvent::WEBMEDIAPLAYER_CREATED: {
-      // Nothing to do here
-      break;
-    }
     case media::MediaLogEvent::PIPELINE_ERROR: {
       int status;
       event.params.GetInteger("pipeline_error", &status);
@@ -289,8 +287,13 @@ void MediaInternals::MediaInternalsUMAHandler::SavePlayerState(
                                &player_info[event.id].video_codec_name);
       }
       if (event.params.HasKey("video_decoder")) {
+        std::string previous_video_decoder(player_info[event.id].video_decoder);
         event.params.GetString("video_decoder",
                                &player_info[event.id].video_decoder);
+        if (!previous_video_decoder.empty() &&
+            previous_video_decoder != player_info[event.id].video_decoder) {
+          player_info[event.id].video_decoder_changed = true;
+        }
       }
       if (event.params.HasKey("video_dds")) {
         event.params.GetBoolean("video_dds", &player_info[event.id].video_dds);
@@ -356,6 +359,12 @@ void MediaInternals::MediaInternalsUMAHandler::ReportUMAForPipelineStatus(
                               player_info.last_pipeline_status,
                               media::PIPELINE_STATUS_MAX + 1);
   }
+  // Report whether video decoder fallback happened, but only if a video decoder
+  // was reported.
+  if (!player_info.video_decoder.empty()) {
+    UMA_HISTOGRAM_BOOLEAN("Media.VideoDecoderFallback",
+                          player_info.video_decoder_changed);
+  }
 }
 
 void MediaInternals::MediaInternalsUMAHandler::LogAndClearPlayersInRenderer(

tools/metrics/histograms/histograms.xml

@@ -12997,6 +12997,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Media.VideoDecoderFallback" enum="BooleanDidFallBack">
+  <owner>watk@chromium.org</owner>
+  <summary>
+    Whether Chrome had to fall back to a secondary video decoder after the
+    primary decoder failed reinitialization.
+  </summary>
+</histogram>
+
 <histogram name="Media.VideoPixelFormat" enum="VideoPixelFormat">
   <owner>scherkus@chromium.org</owner>
   <summary>Pixel format used in HTML5 video. Emitted on video load.</summary>
@@ -42963,6 +42971,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="1" label="Did evict"/>
 </enum>
 
+<enum name="BooleanDidFallBack" type="int">
+  <int value="0" label="Did not fall back"/>
+  <int value="1" label="Did fall back"/>
+</enum>
+
 <enum name="BooleanDistillable" type="int">
   <int value="0" label="Not distillable"/>
   <int value="1" label="Distillable"/>