Added UMA stat for tracking accidental navigations on double tap.

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 495308e9964c327e73ef6e5472a16ed10ed8e36a..92ad1dd555631f5455a6bfc449a2766d4621c583 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3282,6 +3282,21 @@ other types of suffix sets.
   <summary>Network error during OAuth2 access token fetch.</summary>
 </histogram>
 
+<histogram name="Event.ActionAfterDoubleTapNoDelay" enum="ActionAfterDoubleTap">
+  <summary>
+    User's first action within 5 seconds after a double tap gesture when gesture
+    tap event delay is disabled.
+  </summary>
+</histogram>
+
+<histogram name="Event.ActionAfterDoubleTapWithDelay"
+    enum="ActionAfterDoubleTap">
+  <summary>
+    User's first action within 5 seconds after a double tap gesture when gesture
+    tap events are delayed.
+  </summary>
+</histogram>
+
 <histogram name="Event.CoalescedCount.Mouse">
   <summary>Number of Mouse events coalesced.</summary>
 </histogram>
@@ -3773,6 +3788,10 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Event.SingleTapType" enum="TapDelayType">
+  <summary>The number of gesture taps that are delayed vs undelayed</summary>

[Alexei Svitkine (slow), 2013/11/02 00:12:39]

This description really needs more context. When is it logged? What does delayed
vs undelayed mean?

[bokan, 2013/11/04 20:01:08]

Added context for all three histograms.

+</histogram>
+
 <histogram name="ExtensionActivity.ContentScript">
   <summary>
     For each pageload, the number of extensions that inject a content script.
@@ -19794,6 +19813,12 @@ other types of suffix sets.
   <int value="2" label="ScrolledMainFrameWithUnacceleratedFixedRootBackground"/>
 </enum>
 
+<enum name="ActionAfterDoubleTap" type="int">
+  <int value="0" label="Navigated Back"/>
+  <int value="1" label="Stopped Navigation"/>
+  <int value="2" label="No Action"/>
+</enum>
+
 <enum name="ActionUponResourceRequest" type="int">
   <int value="0" label="Load resource"/>
   <int value="1" label="Revalidate resource"/>
@@ -28062,6 +28087,11 @@ other types of suffix sets.
   <int value="1" label="Revisit"/>
 </enum>
 
+<enum name="TapDelayType" type="int">
+  <int value="0" label="Delayed Tap"/>
+  <int value="1" label="Undelayed Tap"/>
+</enum>
+
 <enum name="TcpSocketStatus" type="int">
   <int value="0" label="Unknown"/>
   <int value="1" label="Fast Connection Return"/>