Histogram to track missing and incomplete tiles

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 f307b5bc899f0cd88267310d676ddc004039399b..a472bb8c964bca42909a250eacfc3f5ecda2849f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -2731,6 +2731,28 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Compositing.RenderPass.AppendQuadData.NumIncompleteTiles">
+  <owner>weiliangc@chromium.org.</owner>
+  <summary>
+    Keeps track of number of incomplete tiles in RenderPass during DrawQuad

[danakj, 2014/07/07 20:06:28]

s/in RenderPass during DrawQuad stage/in a drawn compositor frame/

[weiliangc, 2014/07/07 22:01:21]

Done.

+    stage while scrolling. This is a rough measurement of ugliness during user
+    interaction. Incomplete tiles are non ideal scaled. A sample is recorded
+    everytime a frame is drawn while a scroll is in progress. Tracking bug
+    381695.
+  </summary>
+</histogram>
+
+<histogram name="Compositing.RenderPass.AppendQuadData.NumMissingTiles">
+  <owner>weiliangc@chromium.org.</owner>
+  <summary>
+    Keeps track of number of missing tiles in RenderPass during DrawQuad stage
+    while scrolling. This is a rough measurement of ugliness during user
+    interaction. Incomplete tiles are checkerboard or solid color. A sample is
+    recorded everytime a frame is drawn while a scroll is in progress. Tracking
+    bug 381695.
+  </summary>
+</histogram>
+
 <histogram name="ConnectivityDiagnostics.ChromeOsSignalStrength"
     units="percent">
   <owner>ebeach@google.com</owner>