Adding UMA to track previews opt outs and blacklist eligibility

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 d8f3522427db0306559120eb7758d28ebbde7b66..b889dda7a95111ffcc6e16e9bb217469892147ac 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -48034,20 +48034,29 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <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.EligibilityReason.Offline"
+    enum="PreviewsEligibleReason">

[tbansal1, 2016/11/08 00:30:52]

s/PreviewsEligibleReason/PreviewsEligibilityReason/
to match the enum name used in the .cc code.

[RyanSturm, 2016/11/08 22:22:29]

Done.

+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    Whether an offline preview was allowed to be shown or the reason the preview
+    could not be shown to the user.
+  </summary>
+</histogram>
+
 <histogram name="Previews.InfoBarAction.LitePage" enum="PreviewsInfoBarAction">
   <owner>bengr@chromium.org</owner>
   <owner>megjablon@chromium.org</owner>
   <summary>
     Samples of user interactions with the previews LitePage &quot;Saved
     data&quot; infobar. These samples include:
 
     Displays of the infobar and clicks on the &quot;Load original&quot; link.
     Whether the infobar was dismissed by navigation or the user clicking on
     &quot;X&quot; close button.
@@ -48080,20 +48089,28 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
 <histogram name="Previews.OptOut.DBRowCount" units="rows">
   <owner>ryansturm@chromium.org</owner>
   <summary>
     The number of rows in the Previews opt out SQLite table at profile startup.
   </summary>
 </histogram>
 
+<histogram name="Previews.OptOut.UserOptedOut.Offline" units="Boolean">
+  <owner>ryansturm@chromium.org</owner>
+  <summary>
+    True if the user opted out of an offline preview. False if the user did not
+    opt out when a preview was shown.
+  </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>
@@ -95950,20 +95967,31 @@ value.
 
 <enum name="PreviewsContextMenuActionLoFi" type="int">
   <int value="0" label="'Load image' context menu item shown"/>
   <int value="1" label="'Load image' context menu item clicked"/>
   <int value="2"
       label="Pages where the user has clicked 'Load image' at least once"/>
   <int value="3" label="'Load images' context menu item shown"/>
   <int value="4" label="'Load images' context menu item clicked"/>
 </enum>
 
+<enum name="PreviewsEligibleReason" type="int">
+  <int value="0" label="Preview Allowed."/>
+  <int value="1" label="Black list not created."/>
+  <int value="2" label="Blacklist data not loaded yet from disk."/>

[tbansal1, 2016/11/08 00:30:52]

"Blacklist" or "Black list"

[RyanSturm, 2016/11/08 22:22:29]

Done.

+  <int value="3" label="User opted out of a preview recently."/>
+  <int value="4" label="User is blacklisted for all hosts."/>
+  <int value="5" label="User is blacklisted for the specific host."/>
+  <int value="6" label="The network quality estimate is not available."/>
+  <int value="7" label="The network is not slow enough to show previews."/>
+</enum>
+
 <enum name="PreviewsInfoBarAction" type="int">
   <int value="0" label="Infobar shown"/>
   <int value="1" label="Infobar 'Load original' clicked"/>
   <int value="2" label="Infobar dismissed by user"/>
   <int value="3" label="Infobar dismissed by navigation"/>
 </enum>
 
 <enum name="PrinterServiceEventType" type="int">
   <int value="0" label="Printer added"/>
   <int value="1" label="Page displayed (Deprecated)"/>