Add UMA stat to track home button and page prefs

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 897e120c7e2a02280e3cfc8d599edff57e305ea5..d7420bc993cf4e3f2d20de36e5854ca57aec7718 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3878,6 +3878,20 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="HomePage.IsHomeButtonEnabled" enum="BooleanEnabled">
+  <summary>
+    Whether or not the Home button is enabled in user preferences when a profile
+    is loaded.
+  </summary>
+</histogram>
+
+<histogram name="HomePage.IsNewTabPage" enum="Boolean">
+  <summary>
+          Whether or not the home page user preference is set to the default NTP

[Mark P, 2013/07/23 22:05:36]

please fix the spacing

+    value when a profile is loaded.
+  </summary>
+</histogram>
+
 <histogram name="HttpCache.EntryLockWait" units="milliseconds">
   <summary>
     The time spent waiting for write lock on a disk cache entry.