Adding UMA to PreviewsDataSavings

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 f306e4efd6977bf52abe6738a3ef10dc6c9ab778..60117251e6fd4f4eb567778d18db1a60e89e4528 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -45907,20 +45907,70 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Prerender.TimeUntilUsed2" units="ms">
   <owner>pasko@chromium.org</owner>
   <summary>
     Time from when a prerendered page is started to when it is first used due to
     user navigation. If the page is never used, it is not included in this
     histogram.
   </summary>
 </histogram>
 
+<histogram name="Previews.ContentLength" units="KB">
+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    The actual data used for a page load using a preview optimization.
+  </summary>
+</histogram>
+
+<histogram name="Previews.DataInflation" units="KB">
+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    The estimated amount that the content was inflated for a page load using a
+    previews optimization. Recorded when a page load using a previews
+    optimization inflates the data used.
+  </summary>
+</histogram>
+
+<histogram name="Previews.DataInflationPercent" units="%">
+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    The estimated percent of data used that a page load would have otherwise
+    cost for a page load using a previews optimization. Recorded when a page
+    load using a previews optimization inflates the data used.
+  </summary>
+</histogram>
+
+<histogram name="Previews.DataSavings" units="KB">
+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    The estimated data savings for a page load using a previews optimization.
+    Recorded when a page load using a previews optimization reduces the data
+    used.
+  </summary>
+</histogram>
+
+<histogram name="Previews.DataSavingsPercent" units="%">
+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    The estimated percent of data savings for a page load using a previews
+    optimization. Recorded when a page load using a previews optimization
+    reduces the data used.
+  </summary>
+</histogram>
+
+<histogram name="Previews.OriginalContentLength" units="KB">
+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    The estimated content length of a page load using a preview optimization.
+  </summary>
+</histogram>
+
 <histogram name="PrinterService.PrinterServiceEvent"
     enum="PrinterServiceEventType">
   <owner>vitalybuka@chromium.org</owner>
   <summary>
     Count of events in PrinterService on ChromeOS related to USB printers.
   </summary>
 </histogram>
 
 <histogram name="PrintPreview.DestinationAction"
     enum="PrintPreviewPrintDestinationBuckets">
@@ -99591,20 +99641,31 @@ To add a new entry, add it with any value and run test to compute valid value.
 </histogram_suffixes>
 
 <histogram_suffixes
     name="DataReductionProxyRequestCompletionErrorCodesMainFrame" separator=".">
   <suffix name="Primary" label="Primary data reduction proxy"/>
   <suffix name="Fallback" label="Fallback data reduction proxy"/>
   <affected-histogram
       name="DataReductionProxy.RequestCompletionErrorCodes.MainFrame"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="DataSaverEnabled" separator=".">
+  <suffix name="DataSaverEnabled" label="Data Saver is enabled"/>
+  <suffix name="DataSaverDisabled" label="Data Saver is disabled"/>
+  <affected-histogram name="Previews.ContentLength"/>
+  <affected-histogram name="Previews.DataInflation"/>
+  <affected-histogram name="Previews.DataInflationPercent"/>
+  <affected-histogram name="Previews.DataSavings"/>
+  <affected-histogram name="Previews.DataSavingsPercent"/>
+  <affected-histogram name="Previews.OriginalContentLength"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="DataUsageReportSubmissionBytes" separator=".">
   <suffix name="Failed"
       label="Platform external data use observer reported the submission as
              failed"/>
   <suffix name="Lost"
       label="Lost before it could be submitted to platform external data use
              observer"/>
   <suffix name="Successful"
       label="Platform external data use observer reported the submission as
              successful"/>