Add UMA stats for SurfaceDrawQuads in SurfaceAggregator.

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 9219acd94b8852b04e91a09afe67e02ebef73400..c07733654ad871564b7781e31b9878632e5e3ffc 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8085,6 +8085,30 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Compositing.SurfaceAggregator.SurfaceDrawQuad.NoActiveFrame">
+  <owner>kylechar@chromium.org</owner>
+  <summary>
+    The number of SurfaceDrawQuads where the surface exists but doesn't have an
+    active CompositorFrame. This is logged for each call to Aggregate().
+  </summary>
+</histogram>
+
+<histogram name="Compositing.SurfaceAggregator.SurfaceDrawQuad.SurfaceMissing">
+  <owner>kylechar@chromium.org</owner>
+  <summary>
+    The number of SurfaceDrawQuads where the surface doesn't exist. This is
+    logged for each call to Aggregate().
+  </summary>
+</histogram>
+
+<histogram name="Compositing.SurfaceAggregator.SurfaceDrawQuad.ValidSurface">
+  <owner>kylechar@chromium.org</owner>
+  <summary>
+    The number of SurfaceDrawQuads where the surface exists and has an active
+    CompositorFrame. This is logged for each call to Aggregate().
+  </summary>
+</histogram>
+
 <histogram name="Conflicts.ConfirmedBadModules" units="modules">
   <owner>chrisha@chromium.org</owner>
   <summary>