Remove some unneeded media.AVDA histograms.

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 1ae8cde5bd0f94ab57c0d7edbdc0c1e907abc65a..b68e3ade86a22343ab0423c94c2774bfcf638ca3 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -23493,6 +23493,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Media.AVDA.MissingFormatChanged" enum="BooleanFormatChanged">
   <owner>liberato@chromium.org</owner>
+  <obsolete>
+    Deprecated 10/2016. No longer needed.
+  </obsolete>
   <summary>
     Number of times that AVDA stopped decoding because MediaCodec failed to
     provide a FORMAT_CHANGED message before sending decoded frames back.  True
@@ -23503,6 +23506,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Media.AVDA.NumAVDAInstances" units="AVDA instances">
   <owner>watk@chromium.org</owner>
+  <obsolete>
+    Deprecated 10/2016. No longer needed.
+  </obsolete>
   <summary>
     The number of concurrently running AndroidVideoDecodeAccelerators. Logged
     during each AVDA initialization.
@@ -23511,6 +23517,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Media.AVDA.VirtualContext" enum="BooleanVirtualContext">
   <owner>liberato@chromium.org</owner>
+  <obsolete>
+    Deprecated 10/2016. No longer needed.
+  </obsolete>
   <summary>
     Number of times that AVDA's deferred rendering encountered a virtual GL
     context.  True counts indicate virtual, false counts indicate not.