Added UMA counters for Android tool-types.

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 dcd94ba86c0b470536ae618f0f7419d4b77045da..5f183469cc9ef45eac14948a041461b60fd20eb7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13517,6 +13517,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Event.AndroidActionDown.ToolType" enum="MotionEventToolType">
+  <owner>mustaq@chromium.org</owner>
+  <summary>
+    Tracks the number of Android MotionEvents with ACTION_DOWN or
+    ACTION_POINTER_DOWN or ACTION_BUTTON_PRESS for each ToolType (unknown,
+    finger, mouse or stylus).
+  </summary>
+</histogram>
+
 <histogram name="Event.CoalescedCount.Mouse">
   <owner>rbyers@chromium.org</owner>
   <summary>Number of Mouse events coalesced.</summary>
@@ -93955,6 +93964,17 @@ value.
   </int>
 </enum>
 
+<enum name="MotionEventToolType" type="int">
+  <summary>The type of tool that triggers a pointer-type MotionEvent.</summary>
+  <int value="0" label="Unknown">Unknown tool type.</int>
+  <int value="1" label="Finger">The tool is a finger (touch).</int>
+  <int value="2" label="Stylus">The tool is a stylus.</int>
+  <int value="3" label="Mouse">The tool is a mouse or trackpad.</int>
+  <int value="4" label="Eraser">
+    The tool is an eraser or a stylus being used in an inverted posture.
+  </int>
+</enum>
+
 <enum name="MouseEventFollowedByClick" type="int">
   <int value="0" label="Missed event before click"/>
   <int value="1" label="Caught event before click"/>