Custom Tabs: add speculation status histograms.

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 85c7346c99aa00051281e232a566e367816cd3da..b85d9eac1a5d1e2ea91ce4bd98fb5244660b49b3 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -9908,6 +9908,25 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="CustomTabs.SpeculationStatusOnStart"
+    enum="CustomTabsSpeculationStatusOnStart">
+  <owner>mattcary@chromium.org</owner>
+  <summary>
+    Recorded only for Android. How a speculation was started or why it was
+    disallowed. This is recorded when a speculation of any kind is requested,
+    and, if allowed, also when the specific kind of speculation is started.
+  </summary>
+</histogram>
+
+<histogram name="CustomTabs.SpeculationStatusOnSwap"
+    enum="CustomTabsSpeculationStatusOnSwap">
+  <owner>mattcary@chromium.org</owner>
+  <summary>
+    Recorded only for Android. Recorded when a speculation is requesting to swap
+    into a visible tab.
+  </summary>
+</histogram>
+
 <histogram name="CustomTabs.Visible" enum="VisibleTab">
   <owner>yusufo@chromium.org</owner>
   <summary>