Precache tracking database

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 06171d6ef76ad0e59058966a475f5d5a7e2b7c7b..02d439d4368671abd5cfce16ab88f927a12f40c2 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13805,6 +13805,27 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Precache.DownloadedNonPrecache" units="KB">
+  <summary>
+    The number of kilobytes that were downloaded over the network for HTTP/HTTPS
+    fetches that were not motivated by precaching.
+  </summary>
+</histogram>
+
+<histogram name="Precache.DownloadedPrecacheMotivated" units="KB">
+  <summary>
+    The number of kilobytes that were downloaded because of precaching.
+  </summary>
+</histogram>
+
+<histogram name="Precache.Saved" units="KB">
+  <summary>
+    The number of kilobytes during user browsing that were served from the
+    cache, but would have been downloaded over a network if precaching was
+    disabled.
+  </summary>
+</histogram>
+
 <histogram name="Prerender.Events" enum="PrerenderHoverEvent">
   <obsolete>
     deprecated May 10 2012
@@ -31733,6 +31754,13 @@ other types of suffix sets.
   <affected-histogram name="Plugin.PpapiPluginLoadResult"/>
 </fieldtrial>
 
+<fieldtrial name="PrecacheCellular" separator=".">
+  <group name="Cellular"
+      label="covers fetches when connected to cellular networks"/>
+  <affected-histogram name="Precache.DownloadedNonPrecache"/>
+  <affected-histogram name="Precache.Saved"/>
+</fieldtrial>
+
 <fieldtrial name="Prefetch">
   <group name="ContentPrefetchPrefetchOff"
       label="Prefetch is completely disabled."/>