Track age and score of snippets that are clicked (along with position).

chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetArticleViewHolder.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetArticleViewHolder.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetArticleViewHolder.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetArticleViewHolder.java
index 54f9e9d5ddcd7c45f7fd59457a5509fe7ae2c273..23546820f2b345a4bee7bd228d0445bff907bd34 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetArticleViewHolder.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetArticleViewHolder.java
@@ -30,6 +30,7 @@ import org.chromium.chrome.browser.ntp.cards.NewTabPageViewHolder;
 
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.util.concurrent.TimeUnit;
 
 /**
  * A class that represents the view for a single card snippet.
@@ -38,6 +39,7 @@ public class SnippetArticleViewHolder extends NewTabPageViewHolder implements Vi
     private static final String TAG = "NtpSnippets";
     private static final String PUBLISHER_FORMAT_STRING = "%s - %s";
     private static final int FADE_IN_ANIMATION_TIME_MS = 300;
+    private static final int[] HISTOGRAM_FOR_POSITIONS = {0, 2, 4, 9};
 
     private final NewTabPageManager mNewTabPageManager;
     private final TextView mHeadlineTextView;
@@ -46,6 +48,8 @@ public class SnippetArticleViewHolder extends NewTabPageViewHolder implements Vi
     private final ImageView mThumbnailView;
 
     private FetchImageCallback mImageCallback;
+    private long mPublishTimestampMilliseconds;
+    private float mScore;
 
     public String mUrl;
     public int mPosition;
@@ -95,6 +99,21 @@ public class SnippetArticleViewHolder extends NewTabPageViewHolder implements Vi
         RecordHistogram.recordSparseSlowlyHistogram("NewTabPage.Snippets.CardClicked", mPosition);
         NewTabPageUma.recordSnippetAction(NewTabPageUma.SNIPPETS_ACTION_CLICKED);
         NewTabPageUma.recordAction(NewTabPageUma.ACTION_OPENED_SNIPPET);
+
+        // Track how the (approx.) position relates to age / score of the snippet that is clicked.
+        long age = System.currentTimeMillis() - mPublishTimestampMilliseconds;
+        recordAge("NewTabPage.Snippets.CardClickedAge", age);
+        recordScore("NewTabPage.Snippets.CardClickedScore", mScore);
+        int startPosition = 0;
+        for (int endPosition : HISTOGRAM_FOR_POSITIONS) {
+            if (mPosition >= startPosition && mPosition <= endPosition) {
+                String suffix = "_" + startPosition + "_" + endPosition;
+                recordAge("NewTabPage.Snippets.CardClickedAge" + suffix, age);
+                recordScore("NewTabPage.Snippets.CardClickedScore" + suffix, mScore);
+                break;
+            }
+            startPosition = endPosition + 1;
+        }
     }
 
     @Override
@@ -109,6 +128,8 @@ public class SnippetArticleViewHolder extends NewTabPageViewHolder implements Vi
         mArticleSnippetTextView.setText(item.mPreviewText);
         mUrl = item.mUrl;
         mPosition = item.mPosition;
+        mPublishTimestampMilliseconds = item.mTimestamp;
+        mScore = item.mScore;
 
         // If there's still a pending thumbnail fetch, cancel it.
         cancelImageFetch();
@@ -146,6 +167,21 @@ public class SnippetArticleViewHolder extends NewTabPageViewHolder implements Vi
         }
     }
 
+    private static void recordAge(String histogramName, long age) {
+        // Negative values (when the time of the device is set inappropriately) provide no value.
+        if (age >= 0) {
+            long maxAge = TimeUnit.HOURS.toMillis(72);

[Alexei Svitkine (slow), 2016/05/20 14:47:58]

Nit: Add a comment that if this were changed, the histogram should be renamed
since it will change the shape of buckets.

[jkrcal, 2016/05/23 10:01:53]

Done.

+            age = Math.min(age, maxAge);

[Alexei Svitkine (slow), 2016/05/20 14:47:58]

Nit: This is not necessary - it's done already internally by the API.

[jkrcal, 2016/05/23 10:01:53]

Done.

+            RecordHistogram.recordCustomTimesHistogram(
+                    histogramName, age, 1, maxAge, TimeUnit.MILLISECONDS, 50);
+        }
+    }
+
+    private static void recordScore(String histogramName, float score) {
+        int recordedScore = Math.min((int) Math.ceil(score), 1000);
+        RecordHistogram.recordCount1000Histogram(histogramName, recordedScore);
+    }
+
     private void cancelImageFetch() {
         if (mImageCallback != null) {
             mImageCallback.cancel();