UMA: Add histogram for young generation handling in V8

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 f7fd8937c039f19f0327adf824671dab93cf2849..440b04f2611aba0ec81d4b1eee4b62c63561e0b0 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -73156,6 +73156,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Reason a scavenge garbage collection was started in V8.</summary>
 </histogram>
 
+<histogram name="V8.GCYoungGenerationHandling" enum="YoungGenerationHandling">
+  <owner>mlippautz@chromium.org</owner>
+  <summary>
+    Type of garbage collection strategy used to collect the young generation.
+  </summary>
+</histogram>
+
 <histogram name="V8.Initializer.LoadV8Snapshot.Result"
     enum="V8InitializerLoadV8SnapshotResult">
   <owner>oth@chromium.org</owner>
@@ -112100,6 +112107,11 @@ value.
   <int value="1" label="XMLHttpRequestSendArrayBufferView"/>
 </enum>
 
+<enum name="YoungGenerationHandling" type="int">
+  <int value="0" label="Regular Scavenge"/>
+  <int value="1" label="Scavenge using fast promotion mode"/>
+</enum>
+
 <enum name="YouTubeRewriteStatus" type="int">
   <int value="0" label="Success">Embed was properly rewritten.</int>
   <int value="1" label="Success, params were rewritten">