Adding histograms for animated CSS properties in histograms.xml

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 80c319a3a27d6c3692566ed2f6551d1d33277015..0913125c508af305b680e92a7cff5102803c765f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5222,6 +5222,21 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Blink.UseCounter.AnimatedCSSProperties"
+    enum="MappedCSSProperties">
+  <owner>rbyers@chromium.org</owner>
+  <summary>
+    Records usage of animated CSS properties used on a page, either statically
+    or dynamically, from the time the page is initialised to when it is closed
+    or navigated away from. Each property is counted at most once per page per
+    view.
+  </summary>
+  <details>
+    This histogram counts CSS properties only when they are animated by a CSS
+    Animation. Refer to Blink.UseCounter.CSSProperties for more details.
+  </details>
+</histogram>
+
 <histogram name="Blink.UseCounter.CSSProperties" enum="MappedCSSProperties">
   <owner>rbyers@chromium.org</owner>
   <summary>
@@ -5267,6 +5282,19 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </details>
 </histogram>
 
+<histogram name="Blink.UseCounter.SVGImage.AnimatedCSSProperties"
+    enum="MappedCSSProperties">
+  <owner>rbyers@chromium.org</owner>
+  <summary>
+    Like Blink.UseCounter.AnimatedCSSProperties but specifically for the case of
+    CSS properties used inside of an SVG image.
+  </summary>
+  <details>
+    This histogram counts usage of animated CSS properties only. Refer to
+    Blink.UseCounter.SVGImage.CSSProperties for details.
+  </details>
+</histogram>
+
 <histogram name="Blink.UseCounter.SVGImage.CSSProperties"
     enum="MappedCSSProperties">
   <owner>rbyers@chromium.org</owner>