[NTP Snippets] 📷 Add placeholders and start caching thumbnails

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 d76bd1c590f129ab676224a86e9a04d31f852eb1..985090986baa848b7aaf4e2b42cacdd571487989 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
@@ -4,6 +4,7 @@
 
 package org.chromium.chrome.browser.ntp.snippets;
 
+import android.os.AsyncTask;
 import android.text.format.DateUtils;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -30,6 +31,7 @@
     public ImageView mThumbnailView;
     public String mUrl;
     public int mPosition;
+    private ThumbnailFetchingTask mThumbnailFetchingTask;
 
     /**
      * Creates the CardView object to display snippets information
@@ -90,7 +92,12 @@ public void onBindViewHolder(NewTabPageListItem article) {
         mUrl = item.mUrl;
         mPosition = item.mPosition;
 
-        item.setThumbnailOnView(mThumbnailView);
+        // If this view has a pending task, it will display the stale thumbnail when it finishes,
+        // so we need to cancel it.
+        if (mThumbnailFetchingTask != null) mThumbnailFetchingTask.cancel(true);
+
+        mThumbnailFetchingTask = new ThumbnailFetchingTask(item, mThumbnailView);
+        mThumbnailFetchingTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
     }
 
     @Override