Add UMA for PurgeAndSuspend.

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 0f9e7c8c3ee7b825d069310ad609f21828a5066d..479760ec46dc92a1fd11bedc3e14cc4cee9f9fc9 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -48479,6 +48479,55 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PurgeAndSuspend.Memory.BlinkGCKB" units="KB">
+  <owner>tasak@google.com</owner>
+  <summary>
+    The memory usage of the BlinkGC allocator after a background renderer is
+    purged and suspended. Note: this metric is for A/B testing.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Memory.DiscardableKB" units="KB">
+  <owner>tasak@google.com</owner>
+  <summary>
+    The memory usage of the discardable memory after a background renderer is
+    purged and suspended. Note: this metric is for A/B testing.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Memory.MallocMB" units="MB">
+  <owner>tasak@google.com</owner>
+  <summary>
+    The memory usage of the malloc after a background renderer is purged and
+    suspended. Note: this metric is for A/B testing.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Memory.PartitionAllocKB" units="KB">
+  <owner>tasak@google.com</owner>
+  <summary>
+    The memory usage of PartitionAlloc after a background renderer is purged and
+    suspended. Note: this metric is for A/B testing.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Memory.TotalAllocatedMB" units="MB">
+  <owner>tasak@google.com</owner>
+  <summary>
+    The sum of the memory usages of PartitionAlloc, malloc, discardable memory,
+    mainThreadIsolate() and BlinkGC allocator after a backgrounded renderer is
+    purged and suspended. Note: this metric is for A/B testing.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Memory.V8MainThreadIsolateMB" units="MB">
+  <owner>tasak@google.com</owner>
+  <summary>
+    The memory usage of mainThreadIsolate() after a backgrounded renderer is
+    purged and suspended. Note: this metric is for A/B testing.
+  </summary>
+</histogram>
+
 <histogram name="PushMessaging.BackgroundBudget">
   <owner>harkness@chromium.org</owner>
   <summary>