Trigger the Snippets Scheduler when Resuming Activities

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetsBridge.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetsBridge.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetsBridge.java
index 4625b133e6d759f246aafcec3dd53b68e7adb4b4..1a92b267e4eab761c7ffb263682edf51e14f1979 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetsBridge.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetsBridge.java
@@ -4,8 +4,11 @@
 
 package org.chromium.chrome.browser.ntp.snippets;
 
+import android.app.Activity;
 import android.graphics.Bitmap;
 
+import org.chromium.base.ActivityState;
+import org.chromium.base.ApplicationStatus;
 import org.chromium.base.Callback;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.chrome.browser.ntp.cards.SuggestionsCategoryInfo;
@@ -179,6 +182,28 @@ public class SnippetsBridge implements SuggestionsSource {
         nativeOnNTPInitialized(mNativeSnippetsBridge);
     }
 
+    /**
+     * Returns a listener creating a bridge to propagate the activity state changes.
+     */
+    public static ApplicationStatus.ActivityStateListener makeActivityStateListener() {
+        return new ApplicationStatus.ActivityStateListener() {
+            @Override
+            public void onActivityStateChange(Activity activity, int newState) {
+                // This event is only triggered when the start was already warm.

[Michael van Ouwerkerk, 2017/01/04 14:32:17]

Are you sure resume only happens for warm starts? That seems to be different
from the documentation which indicates it happens as part of activity creation
and startup: https://developer.android.com/reference/android/app/Activity.html

[fhorschig, 2017/01/04 15:04:44]

I was really surprised to notice this. This might be a flaw of the listener,
or it is registered to late.
I introduced a check for the loaded library for the case that this behavior
should ever change.

+                if (newState == ActivityState.RESUMED) {
+                    SnippetsBridge snippetsBridge =
+                            new SnippetsBridge(Profile.getLastUsedProfile());
+                    snippetsBridge.onWarmStartedActivityResumed();
+                }
+            }
+        };
+    }
+
+    public static void notifySchedulerAboutColdStart() {
+        SnippetsBridge snippetsBridge = new SnippetsBridge(Profile.getLastUsedProfile());
+        snippetsBridge.onColdStart();
+    }
+
     public static void onSuggestionTargetVisited(int category, long visitTimeMs) {
         nativeOnSuggestionTargetVisited(category, visitTimeMs);
     }
@@ -208,6 +233,16 @@ public class SnippetsBridge implements SuggestionsSource {
         nativeFetch(mNativeSnippetsBridge, category, displayedSuggestionIds);
     }
 
+    private void onWarmStartedActivityResumed() {
+        assert mNativeSnippetsBridge != 0;
+        nativeOnWarmStartedActivityResumed(mNativeSnippetsBridge);
+    }
+
+    private void onColdStart() {
+        assert mNativeSnippetsBridge != 0;
+        nativeOnColdStart(mNativeSnippetsBridge);
+    }
+
     @CalledByNative
     private static List<SnippetArticle> createSuggestionList() {
         return new ArrayList<>();
@@ -312,6 +347,8 @@ public class SnippetsBridge implements SuggestionsSource {
             long nativeNTPSnippetsBridge, int category, int position);
     private native void nativeOnMoreButtonClicked(
             long nativeNTPSnippetsBridge, int category, int position);
+    private native void nativeOnWarmStartedActivityResumed(long nativeNTPSnippetsBridge);
+    private native void nativeOnColdStart(long nativeNTPSnippetsBridge);
     private static native void nativeOnSuggestionTargetVisited(int category, long visitTimeMs);
     private static native void nativeOnNTPInitialized(long nativeNTPSnippetsBridge);
     private native void nativeSetObserver(long nativeNTPSnippetsBridge, SnippetsBridge bridge);