Add new NTP layout with snippet cards and hide it behind a flag

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 64df7d0bf5ecc2e80aad60215441f03e8382f19b..39e075b1f9d07f60a90663fff6ec2d257fd5078a 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
@@ -7,6 +7,9 @@
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.chrome.browser.profiles.Profile;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * Provides access to the snippets to display on the NTP using the C++ NTP Snippets Service
  */
@@ -14,14 +17,13 @@
     private static final String TAG = "SnippetsBridge";
 
     private long mNativeSnippetsBridge;
+    private SnippetsObserver mObserver;
 
     /**
      * An observer for notifying when new snippets are loaded
      */
     public interface SnippetsObserver {
-        @CalledByNative("SnippetsObserver")
-        public void onSnippetsAvailable(
-                String[] titles, String[] urls, String[] thumbnailUrls, String[] previewText);
+        public void onSnippetsReceived(List<SnippetArticle> snippets);

[newt (away), 2016/03/30 19:03:50]

This is a much cleaner public interface :)

     }
 
     /**
@@ -29,28 +31,39 @@ public void onSnippetsAvailable(
      *
      * @param profile Profile of the user that we will retrieve snippets for.
      */
-    public SnippetsBridge(Profile profile, final SnippetsObserver observer) {
+    public SnippetsBridge(Profile profile) {
         mNativeSnippetsBridge = nativeInit(profile);
-        SnippetsObserver wrappedObserver = new SnippetsObserver() {
-            @Override
-            public void onSnippetsAvailable(
-                    String[] titles, String[] urls, String[] thumbnailUrls, String[] previewText) {
-                // Don't notify observer if we've already been destroyed.
-                if (mNativeSnippetsBridge != 0) {
-                    observer.onSnippetsAvailable(titles, urls, thumbnailUrls, previewText);
-                }
-            }
-        };
-        nativeSetObserver(mNativeSnippetsBridge, wrappedObserver);
     }
 
-    void destroy() {
+    public void destroy() {

[newt (away), 2016/03/30 19:03:50]

javadoc

[dgn, 2016/03/31 00:46:45]

Done.

         assert mNativeSnippetsBridge != 0;
         nativeDestroy(mNativeSnippetsBridge);
         mNativeSnippetsBridge = 0;
     }
 
+    public void setObserver(SnippetsObserver observer) {

[newt (away), 2016/03/30 19:03:50]

javadoc. Worth mentioning that this should only be called once.

[dgn, 2016/03/31 00:46:45]

Done.

+        assert mObserver == null;
+
+        mObserver = observer;
+        nativeSetObserver(mNativeSnippetsBridge, this);
+    }
+
+    @CalledByNative
+    private void onSnippetsAvailable(String[] titles, String[] urls, String[] thumbnailUrls,
+            String[] previewText, long[] timestamps) {
+        // Don't notify observer if we've already been destroyed.
+        if (mNativeSnippetsBridge == 0) return;
+
+        List<SnippetArticle> newSnippets = new ArrayList<>(titles.length);
+        for (int i = 0; i < titles.length; i++) {
+            newSnippets.add(new SnippetArticle(
+                    titles[i], "", previewText[i], urls[i], thumbnailUrls[i], timestamps[i], i));
+        }
+
+        mObserver.onSnippetsReceived(newSnippets);

[newt (away), 2016/03/30 19:03:50]

mObserver could be null here. (at least with the current public interface)

[dgn, 2016/03/31 00:46:45]

The method can be called from the native side only if the observer has been set
(NTPSnippetsServiceLoaded returns early when it's not) so it's safe from the
point of view of the initialization. For the destruction, mNativeSnippetsBridge
covers it. Mentioned that in the javadoc for setObserver.

+    }
+
     private native long nativeInit(Profile profile);
     private native void nativeDestroy(long nativeNTPSnippetsBridge);

[newt (away), 2016/03/30 19:03:50]

nit: s/NTP/Ntp/

In Java code, even acronyms should be camelCased in names. "Ui", "Http", etc

[dgn, 2016/03/31 00:46:45]

That refers to the c++ class name, can't be modified.

-    private native void nativeSetObserver(long nativeNTPSnippetsBridge, SnippetsObserver observer);
+    private native void nativeSetObserver(long nativeNTPSnippetsBridge, SnippetsBridge bridge);
 }