Additional tracing and histogram in Extensions startup.

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 1f090b01498b2db69562cbfbddb134e109d5f5c5..6b7927080b186615879df27e37c52b1d9dc5c576 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8700,6 +8700,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Extensions.ExtensionManagement_RefreshTime"
+    units="milliseconds">
+  <owner>rkaplow@chromium.org</owner>
+  <summary>
+    The amount of time that elapsed during ExtensionManagement::Refresh.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.ExtensionRootPathLength">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
@@ -41153,8 +41161,8 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <owner>ulan@chromium.org</owner>
   <summary>
     Number of garbage collections that a detached global context survives,
-    recorded after each major garbage collection.
-    Values greater than 7 indicate a memory leak.
+    recorded after each major garbage collection. Values greater than 7 indicate
+    a memory leak.
   </summary>
 </histogram>