Refine tracking of snippet dismissals.

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 245a3c456c67f607c92a2a1ddd71e317d91cb9db..961187167ab59c29a6f9d034eb5f5194b1ae1073 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
@@ -62,7 +62,7 @@ public class NewTabPageUma {
 
     /** Possible interactions with the snippets. */
     @IntDef({SNIPPETS_ACTION_SHOWN, SNIPPETS_ACTION_SCROLLED, SNIPPETS_ACTION_CLICKED,
-            SNIPPETS_ACTION_DISMISSED})
+            SNIPPETS_ACTION_DISMISSED_VISITED, SNIPPETS_ACTION_DISMISSED_UNVISITED})
     @Retention(RetentionPolicy.SOURCE)
     public @interface SnippetsAction {}
     /** Snippets are enabled and are being shown to the user. */
@@ -71,10 +71,12 @@ public class NewTabPageUma {
     public static final int SNIPPETS_ACTION_SCROLLED = 1;
     /** A snippet has been clicked. */
     public static final int SNIPPETS_ACTION_CLICKED = 2;
-    /** A snippet has been swiped away. */
-    public static final int SNIPPETS_ACTION_DISMISSED = 3;
+    /** A snippet has been swiped away, it had been viewed by the user (on this device). */
+    public static final int SNIPPETS_ACTION_DISMISSED_VISITED = 3;

[Bernhard Bauer, 2016/04/21 16:19:27]

Try not to change the semantics of existing UMA actions. Just add new ones
instead and remove the old ones if they're not necessary anymore -- that's the
reason why we specify explicit values.

[PEConn, 2016/04/21 16:35:40]

Done.

+    /** A snippet has been swiped away, it had not been viewed by the user (on this device). */
+    public static final int SNIPPETS_ACTION_DISMISSED_UNVISITED = 4;
     /** The number of possible actions. */
-    private static final int NUM_SNIPPETS_ACTIONS = 4;
+    private static final int NUM_SNIPPETS_ACTIONS = 5;
 
     /**
      * Records an action taken by the user on the NTP.