Add UMA logging to track bad MIME types passed to HTMLMediaElement

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 3670e9d20f50d763404c55cd8b62b1dead75b309..5b6ee07b2f4f9c77fa131bc32be6dc33aa4fa931 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -26616,6 +26616,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.MediaElement.ContentTypeParseable"
+    enum="ContentTypeParseableResult">
+  <owner>jrummell@chromium.org</owner>
+  <summary>
+    Whether the content type provided to HTMLMediaElement would parse with
+    ParsedContentType or not.
+  </summary>
+</histogram>
+
 <histogram name="Media.MicrophoneMuted" enum="MicrophoneMuteResult">
   <owner>henrika@chromium.org</owner>
   <summary>
@@ -85152,6 +85161,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="26" label="Background sync setting"/>
 </enum>
 
+<enum name="ContentTypeParseableResult" type="int">
+  <int value="0" label="IsSupported returned and MIME type parseable"/>
+  <int value="1" label="MayBeSupported returned and MIME type parseable"/>
+  <int value="2" label="IsNotSupported returned and MIME type parseable"/>
+  <int value="3"
+      label="IsSupported returned and MIME type not parseable (should fail)"/>
+  <int value="4"
+      label="MayBeSupported returned and MIME type not parseable (should
+             fail)"/>
+  <int value="5"
+      label="IsNotSupported returned and MIME type not parseable (acceptable)"/>
+</enum>
+
 <enum name="ContextLostReason" type="int">
   <summary>The reason for losing a GPU context.</summary>
   <int value="0" label="CONTEXT_INIT_FAILED"/>