Add histograms for animated image types

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 540d233bcb7d01c985ffcb88cdeccdff6f0ca59e..92f6c6d3af5ef1d2e52fc98fa7f47145ae5d727a 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4490,6 +4490,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Records whenever a Blimp tab toggles visibility.</summary>
 </histogram>
 
+<histogram name="Blink.AnimatedImageType" enum="AnimatedImageType">
+  <owner>scroggo@chromium.org</owner>
+  <summary>
+    Type of encoded image used for animation. Logged during parsing, which
+    typically happens twice per animated image on the page.
+  </summary>
+</histogram>
+
 <histogram name="Blink.Binding.InitializeMainWindowProxy" units="microseconds">
   <owner>peria@chromium.org</owner>
   <summary>
@@ -80841,6 +80849,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="4" label="Undos Dismissed (Action) (Deprecated)"/>
 </enum>
 
+<enum name="AnimatedImageType" type="int">
+  <int value="0" label="kAnimatedGIF"/>
+  <int value="1" label="kAnimatedWebP"/>
+  <int value="2" label="kAnimatedPNG"/>
+</enum>
+
 <enum name="AntiVirusMetricsProviderResult" type="int">
   <int value="0" label="RESULT_SUCCESS"/>
   <int value="1" label="RESULT_GENERIC_FAILURE"/>