Add UMA histogram for save link file type

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 9d6c163acca5807d32a8c319d7c52d73e7822f0c..6106b756183eb2a511c33f1c0074cf3285e678a5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5199,6 +5199,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ContextMenu.SaveLinkType" enum="ContextMenuSaveLinkType">
+  <owner>qinmin@chromium.org</owner>
+  <summary>
+    Type of the url when user saves the content through the save link context
+    menu.
+  </summary>
+</histogram>
+
 <histogram name="ContextMenu.SelectedOption" enum="ContextMenuOption">
   <owner>newt@chromium.org</owner>
   <summary>The option that the user selected from a context menu.</summary>
@@ -56321,6 +56329,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="19" label="Share image"/>
 </enum>
 
+<enum name="ContextMenuSaveLinkType" type="int">
+  <summary>
+    The content type when user chooses save link context menu option
+  </summary>
+  <int value="0" label="Unkown"/>
+  <int value="1" label="Text"/>
+  <int value="2" label="Image"/>
+  <int value="3" label="Audio"/>
+  <int value="4" label="Video"/>
+  <int value="5" label="Pdf"/>
+</enum>
+
 <enum name="ContextualSearchIconSpriteAnimated" type="int">
   <int value="0" label="Animated, seen, from tap"/>
   <int value="1" label="Animated, not seen, from tap"/>