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 6b69d15098bbb3cd6b13596f615eeb8bff1cef59..7d9fad4b8fd26e7ee590b87d5bfd344530ed61fe 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13714,6 +13714,44 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Precache.DailyDownloadedNonPrecacheKB" units="KB">
+  <summary>
+    The number of kilobytes that were downloaded over the network for HTTP/HTTPS
+    fetches that were not motivated by precaching. This metric is accumulated
+    over 24 hour intervals, and can cover multiple sessions. Values of this
+    metric for previous, unreported 24 hour intervals are reported at the start
+    of a precaching cycle.
+  </summary>
+</histogram>
+
+<histogram name="Precache.DailyDownloadedPrecacheMotivatedKB" units="KB">
+  <summary>
+    The number of kilobytes that were downloaded because of precaching. This
+    metric is accumulated over 24 hour intervals, and can cover multiple
+    sessions. Values of this metric for previous, unreported 24 hour intervals
+    are reported at the start of a precaching cycle.
+  </summary>
+</histogram>
+
+<histogram name="Precache.DailySavedKB" 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. This metric is accumulated over 24 hour intervals, and can cover
+    multiple sessions. Values of this metric for previous, unreported 24 hour
+    intervals are reported at the start of a precaching cycle.
+  </summary>
+</histogram>
+
+<histogram name="Precache.DailySavingsPercentage" units="%">
+  <summary>
+    The percentage of user browsing network bandwidth that was saved because of
+    precaching. This metric is accumulated over 24 hour intervals, and can cover
+    multiple sessions. Values of this metric for previous, unreported 24 hour
+    intervals are reported at the start of a precaching cycle.
+  </summary>
+</histogram>
+
 <histogram name="Prerender.Events" enum="PrerenderHoverEvent">
   <obsolete>
     deprecated May 10 2012
@@ -31507,6 +31545,14 @@ 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.DailyDownloadedNonPrecacheKB"/>
+  <affected-histogram name="Precache.DailySavedKB"/>
+  <affected-histogram name="Precache.DailySavingsPercentage"/>
+</fieldtrial>
+
 <fieldtrial name="Prefetch">
   <group name="ContentPrefetchPrefetchOff"
       label="Prefetch is completely disabled."/>