📰 UMA to track how long the placeholder is displayed

Bug: 664578
Change-Id: I47437bd37bd3581d070c72c8fe977cc457d81214
Reviewed-on: https://chromium-review.googlesource.com/686875Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Jan Krcal <jkrcal@chromium.org>
Commit-Queue: Nicolas Dossou-Gbété <dgn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505080}

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java

@@ -418,9 +418,10 @@ public class SuggestionsSection extends InnerNode {
         return suggestionIds;
     }
 
-    private void updatePlaceholderVisibility() {
-        if (!FeatureUtilities.isChromeHomeEnabled()) return;
+    private boolean updatePlaceholderVisibility() {
+        if (!FeatureUtilities.isChromeHomeEnabled()) return false;
         mPlaceholder.setVisible(isLoading() && !hasSuggestions());
+        return mPlaceholder.isVisible();
     }
 
     /**
@@ -575,7 +576,9 @@ public class SuggestionsSection extends InnerNode {
 
         boolean isLoading = SnippetsBridge.isCategoryLoading(status);
         mMoreButton.updateState(isLoading ? ActionItem.State.LOADING : ActionItem.State.BUTTON);
-        updatePlaceholderVisibility();
+        if (updatePlaceholderVisibility()) {
+            mPlaceholder.trackVisibilityDuration();
+        }
     }
 
     /** Clears the suggestions and related data, resetting the state of the section. */

chrome/android/java/src/org/chromium/chrome/browser/suggestions/ContentSuggestionPlaceholder.java

@@ -13,6 +13,7 @@ import org.chromium.chrome.browser.ntp.cards.ItemViewType;
 import org.chromium.chrome.browser.ntp.cards.NewTabPageViewHolder;
 import org.chromium.chrome.browser.ntp.cards.NodeVisitor;
 import org.chromium.chrome.browser.ntp.cards.OptionalLeaf;
+import org.chromium.chrome.browser.suggestions.SuggestionsMetrics.DurationTracker;
 import org.chromium.chrome.browser.widget.displaystyle.UiConfig;
 
 /**
@@ -22,8 +23,20 @@ public class ContentSuggestionPlaceholder extends OptionalLeaf {
     /** Color used to fill highlighted empty UI elements of the placeholder. */
     private static final @ColorRes int HIGHLIGHT_COLOR = R.color.black_alpha_20;
 
+    private final DurationTracker mVisibilityDurationTracker =
+            SuggestionsMetrics.getPlaceholderVisibilityReporter();
+
     public void setVisible(boolean visible) {
         setVisibilityInternal(visible);
+        if (!visible) mVisibilityDurationTracker.endTracking();
+    }
+
+    /**
+     * Start tracking how long we show the placeholder. When it is hidden, it will report that
+     * duration through UMA.
+     */
+    public void trackVisibilityDuration() {
+        mVisibilityDurationTracker.startTracking();
     }
 
     @Override

chrome/android/java/src/org/chromium/chrome/browser/suggestions/SuggestionsMetrics.java

@@ -90,15 +90,12 @@ public abstract class SuggestionsMetrics {
     public static void recordVisit(Tab tab, SnippetArticle suggestion) {
         @CategoryInt
         final int category = suggestion.mCategory;
-        NavigationRecorder.record(tab, new Callback<NavigationRecorder.VisitData>() {
-            @Override
-            public void onResult(NavigationRecorder.VisitData visit) {
-                if (NewTabPage.isNTPUrl(visit.endUrl)) {
-                    RecordUserAction.record("MobileNTP.Snippets.VisitEndBackInNTP");
-                }
-                RecordUserAction.record("MobileNTP.Snippets.VisitEnd");
-                SuggestionsEventReporterBridge.onSuggestionTargetVisited(category, visit.duration);
+        NavigationRecorder.record(tab, visit -> {
+            if (NewTabPage.isNTPUrl(visit.endUrl)) {
+                RecordUserAction.record("MobileNTP.Snippets.VisitEndBackInNTP");
             }
+            RecordUserAction.record("MobileNTP.Snippets.VisitEnd");
+            SuggestionsEventReporterBridge.onSuggestionTargetVisited(category, visit.duration);
         });
     }
 
@@ -135,6 +132,18 @@ public abstract class SuggestionsMetrics {
                 MostVisitedSitesBridge.MAX_TILE_COUNT);
     }
 
+    /**
+     * @return A {@link DurationTracker} to notify to report how long the placeholder is visible
+     * for.
+     */
+    public static DurationTracker getPlaceholderVisibilityReporter() {
+        return new DurationTracker((duration) -> {
+            RecordHistogram.recordTimesHistogram(
+                    "ContentSuggestions.FetchPendingPlaceholder.VisibleDuration", duration,
+                    TimeUnit.MILLISECONDS);
+        });
+    }
+
     /**
      * Measures the amount of time it takes for date formatting in order to track StrictMode
      * violations.
@@ -165,4 +174,33 @@ public abstract class SuggestionsMetrics {
             mFired = false;
         }
     }
+
+    /**
+     * Utility class to track the duration of an event. Call {@link #startTracking()} and
+     * {@link #endTracking()} to notify about the key moments. These methods are no-ops when called
+     * while tracking is not in the expected state.
+     */
+    public static class DurationTracker {
+        private long mTrackingStartTimeMs;
+        private final Callback<Long> mTrackingCompleteCallback;
+
+        private DurationTracker(Callback<Long> trackingCompleteCallback) {
+            mTrackingCompleteCallback = trackingCompleteCallback;
+        }
+
+        public void startTracking() {
+            if (isTracking()) return;
+            mTrackingStartTimeMs = System.currentTimeMillis();
+        }
+
+        public void endTracking() {
+            if (!isTracking()) return;
+            mTrackingCompleteCallback.onResult(System.currentTimeMillis() - mTrackingStartTimeMs);
+            mTrackingStartTimeMs = 0;
+        }
+
+        private boolean isTracking() {
+            return mTrackingStartTimeMs > 0;
+        }
+    }
 }

tools/metrics/histograms/histograms.xml

@@ -10361,6 +10361,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ContentSuggestions.FetchPendingPlaceholder.VisibleDuration"
+    units="ms">
+  <owner>dgn@chromium.org</owner>
+  <owner>ntp-dev+metrics@chromium.org</owner>
+  <summary>
+    Android: How long the content suggestion placeholder is shown. This is
+    tracked based on when the placeholder is enabled in the UI, not how long it
+    is actually visible on screen. Depending on the screen size, the used value
+    could be bigger.
+  </summary>
+</histogram>
+
 <histogram name="ContextMenu.SaveLinkType" enum="ContextMenuSaveLinkType">
   <owner>qinmin@chromium.org</owner>
   <summary>