Metrics for user interests shown on the NTP.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/InterestsPage.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/InterestsPage.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/InterestsPage.java
index edea4d841e66c2f9d5b371e93bc91f0852dbed53..61ca388e2cf02bac305cb64a9f91bcccdcf7dace 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/InterestsPage.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/InterestsPage.java
@@ -10,6 +10,8 @@ import android.view.LayoutInflater;
 import android.view.View;
 
 import org.chromium.base.ApiCompatibilityUtils;
+import org.chromium.base.metrics.RecordHistogram;
+import org.chromium.base.metrics.RecordUserAction;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.NativePage;
 import org.chromium.chrome.browser.UrlConstants;
@@ -35,6 +37,8 @@ public class InterestsPage implements NativePage {
     private final int mBackgroundColor;
     private final int mThemeColor;
 
+    private boolean mClicked;
+
     /**
      * Creates a InterestsPage to be shown in document mode.
      *
@@ -57,21 +61,39 @@ public class InterestsPage implements NativePage {
                 new GetInterestsCallback() {
                     @Override
                     public void onInterestsAvailableCallback(Interest[] interests) {
-                        if (interests == null) {
-                            Toast toast = Toast.makeText(context,
-                                    R.string.ntp_no_interests_toast, Toast.LENGTH_SHORT);
-                            toast.show();
+                        boolean gotInterests = interests != null;
+                        RecordHistogram.recordBooleanHistogram(
+                                "NewTabPage.Interests.InterestsFetchSuccess", gotInterests);
+                        if (!gotInterests) {
+                            showToastOnFailure();
                             return;
                         }
                         List<Interest> interestList = Arrays.asList(interests);
-
+                        RecordHistogram.recordSparseSlowlyHistogram(
+                                "NewTabPage.Interests.NumInterests", interestList.size());

[Alexei Svitkine (slow), 2015/12/09 16:15:57]

Why sparse and not counts?

[knn, 2015/12/10 06:57:17]

The same rationale as when we discussed NewTabPage.Snippets.NumArticles,
NewTabPage.NumberOfTiles:
Prefer exact counts
Number of items < 30
Number should be roughly constant for a user
Sparse histograms seem cleaner than putting artificial bounds like here
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ui/...
which will have to be updated if the number of items changes like due to the
IconNTP experiment.

[Alexei Svitkine (slow), 2015/12/10 16:13:47]

Please add a comment about this above the function call. Despite this making
sense in this case, it's generally unconventional to use sparse histograms for
counts, so its worth having a comment to indicate this is intentional (and why
it's ok to do).

[knn, 2015/12/17 05:30:01]

Done.

+                        if (interestList.size() == 0) {
+                            showToastOnFailure();
+                            return;
+                        }
                         mPageView.setInterests(interestList);
                     }
+
+                    private void showToastOnFailure() {
+                        Toast.makeText(context, R.string.ntp_no_interests_toast, Toast.LENGTH_SHORT)
+                                .show();
+                    }
                 });
     }
 
-    public void setListener(InterestsClickListener listener) {
-        mPageView.setListener(listener);
+    public void setListener(final InterestsClickListener listener) {
+        mPageView.setListener(new InterestsClickListener() {
+            public void onInterestClicked(String interest) {
+                mClicked = true;
+                NewTabPageUma.recordAction(NewTabPageUma.ACTION_CLICKED_INTEREST);
+                RecordUserAction.record("MobileNTP.Interests.Click");
+                listener.onInterestClicked(interest);
+            }
+        });
     }
 
     /**
@@ -108,6 +130,8 @@ public class InterestsPage implements NativePage {
 
     @Override
     public void destroy() {
+        if (mClicked) return;
+        RecordUserAction.record("MobileNTP.Interests.Dismissed");
     }
 
     @Override