customtabs: Histograms for special sessions prerendering.

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 8ff974880e85f5cec62e134926ff133de736a928..6898a14ff6f09b31957332dfca7a661acbceece6 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -7309,6 +7309,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="CustomTabs.NonDefaultSessionPrerenderMatched"
+    enum="BooleanMatched">
+  <owner>lizeb@chromium.org</owner>
+  <summary>
+    Android: When there is a prerender for a session with non-default
+    parameters, whether the prerender was matched when navigating.
+  </summary>
+</histogram>
+
 <histogram name="CustomTabs.PredictionStatus" enum="PredictionStatus">
   <owner>lizeb@chromium.org</owner>
   <summary>
@@ -7325,6 +7334,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="CustomTabs.PrerenderSessionUsesDefaultParameters"
+    enum="BooleanDefault">
+  <owner>lizeb@chromium.org</owner>
+  <summary>
+    Android: When prerendering a URL for Custom Tabs, whether the client session
+    uses the default parameters.
+  </summary>
+</histogram>
+
 <histogram name="CustomTabs.Visible" enum="VisibleTab">
   <owner>yusufo@chromium.org</owner>
   <summary>
@@ -67984,6 +68002,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Data Reduction Proxy"/>
 </enum>
 
+<enum name="BooleanDefault" type="int">
+  <int value="0" label="Not Default"/>
+  <int value="1" label="Default"/>
+</enum>
+
 <enum name="BooleanDeferred" type="int">
   <int value="0" label="Not deferred"/>
   <int value="1" label="Deferred"/>