memory metrics: record growth after purging BG renderer's cache

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 f6d9fe998e9b04f9bba23492153b20f9c9614cf9..c30b9a1e998c1a3bb0b9dc98de66a70f4c6fd145 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -51739,6 +51739,59 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PurgeAndSuspend.Experimental.MemoryGrowth.BlinkGCKB"
+    units="KB">
+  <owner>tasak@google.org</owner>
+  <summary>
+    The memory growth of the BlinkGC allocator after a background renderer is
+    purged.

[Ilya Sherman, 2017/01/19 02:26:09]

Please document when this is recorded -- i.e. 5, 10, and 15 minutes after the
purge (right?)

[tasak, 2017/01/19 05:13:53]

Right.
Done.

+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Experimental.MemoryGrowth.DiscardableKB"
+    units="KB">
+  <owner>tasak@google.org</owner>
+  <summary>
+    The memory growth of the discardable memory after a background renderer is
+    purged.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Experimental.MemoryGrowth.MallocMB" units="MB">
+  <owner>tasak@google.org</owner>
+  <summary>
+    The memory growth of the malloc after a background renderer is purged.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Experimental.MemoryGrowth.PartitionAllocKB"
+    units="KB">
+  <owner>tasak@google.org</owner>
+  <summary>
+    The memory growth of PartitionAlloc after a background renderer is purged.
+  </summary>
+</histogram>
+
+<histogram name="PurgeAndSuspend.Experimental.MemoryGrowth.TotalAllocatedMB"
+    units="MB">
+  <owner>tasak@google.org</owner>
+  <summary>
+    The total memory growth of the allocators: PartitionAlloc, malloc,
+    discardable memory, mainThreadIsolate() and BlinkGC after a backgrounded
+    renderer is purged.
+  </summary>
+</histogram>
+
+<histogram
+    name="PurgeAndSuspend.Experimental.MemoryGrowth.V8MainThreadIsolateMB"
+    units="MB">
+  <owner>tasak@google.org</owner>
+  <summary>
+    The memory growth of mainThreadIsolate() after a backgrounded renderer is
+    purged.
+  </summary>
+</histogram>

[Ilya Sherman, 2017/01/19 02:26:09]

Please use histogram_suffixes to reduce the amount of repetition in this file.

[tasak, 2017/01/19 05:13:53]

Done.

+
 <histogram name="PurgeAndSuspend.Memory.BlinkGCKB" units="KB">
   <owner>tasak@google.com</owner>
   <summary>