[NTP Snippets] Add UMA for snippet dismissal

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageUma.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageUma.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageUma.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageUma.java
index fd4ca3d5b5c7d9d6288c60fef1ab6bef0683717f..2238947b5f4a5ccf459ecbd844ea9dbf117a1aa4 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageUma.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageUma.java
@@ -61,7 +61,8 @@
     private static final int NUM_NTP_IMPRESSION = 2;
 
     /** Possible interactions with the snippets. */
-    @IntDef({SNIPPETS_ACTION_SHOWN, SNIPPETS_ACTION_SCROLLED, SNIPPETS_ACTION_CLICKED})
+    @IntDef({SNIPPETS_ACTION_SHOWN, SNIPPETS_ACTION_SCROLLED, SNIPPETS_ACTION_CLICKED,
+            SNIPPETS_ACTION_DISMISSED})
     @Retention(RetentionPolicy.SOURCE)
     public @interface SnippetsAction {}
     /** Snippets are enabled and are being shown to the user. */
@@ -70,8 +71,10 @@
     public static final int SNIPPETS_ACTION_SCROLLED = 1;
     /** A snippet has been clicked. */
     public static final int SNIPPETS_ACTION_CLICKED = 2;
+    /** A snippet as been swiped. */

[Bernhard Bauer, 2016/04/14 15:36:34]

Nit: "has". 

[dgn, 2016/04/15 10:51:57]

Done.

+    public static final int SNIPPETS_ACTION_DISMISSED = 3;
     /** The number of possible actions. */
-    private static final int NUM_SNIPPETS_ACTIONS = 3;
+    private static final int NUM_SNIPPETS_ACTIONS = 4;
 
     /**
      * Records an action taken by the user on the NTP.