Adding UMA stats for dragdrop events for both touch and mouse.

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 7964d1431c3354ab667643c8036a2c8b3bcfdfcd..4bf48d3889fa22d3c584081668b66a58df5b5556 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6092,6 +6092,35 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>The write size for calls to BaseFile::AppendDataTofile().</summary>
 </histogram>
 
+<histogram name="DragDrop.Cancel" enum="DragDropEventSource">
+  <owner>mfomitchev@chromium.org</owner>
+  <summary>
+    Counts the number of times the user cancelled a drag and drop operation.
+  </summary>
+</histogram>
+
+<histogram name="DragDrop.Drop" enum="DragDropEventSource">
+  <owner>mfomitchev@chromium.org</owner>
+  <summary>
+    Counts the number of times the user completed a drag and drop operation.
+  </summary>
+</histogram>
+
+<histogram name="DragDrop.ExternalOriginDrop">
+  <owner>mfomitchev@chromium.org</owner>
+  <summary>
+    Counts the number of times a drag and drop operation originating outside of
+    a chrome window successfuly drops.
+  </summary>
+</histogram>
+
+<histogram name="DragDrop.Start" enum="DragDropEventSource">
+  <owner>mfomitchev@chromium.org</owner>
+  <summary>
+    Counts the number of times the user started a drag and drop operation.
+  </summary>
+</histogram>
+
 <histogram name="Drive.CacheDBOpenStatus" enum="DriveCacheDBOpenStatus">
   <obsolete>
     Deprecated 8/2013.
@@ -44764,6 +44793,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="4" label="Initiated by Resumption"/>
 </enum>
 
+<enum name="DragDropEventSource" type="int">
+  <int value="0" label="Mouse"/>
+  <int value="1" label="Touch"/>
+</enum>
+
 <enum name="DriveCacheDBOpenStatus" type="int">
   <int value="0" label="Success"/>
   <int value="1" label="Corrupt database"/>