[Feed] Capture thumbnail for Feed NTP

Bug: 860037
Change-Id: I1df221b8ec11c212c1fb4db0f7430f9daadaaa54
Reviewed-on: https://chromium-review.googlesource.com/1158995Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579942}

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/FeedNewTabPage.java

@@ -254,15 +254,14 @@ public class FeedNewTabPage extends NewTabPage implements TouchEnabledDelegate {
 
     @Override
     public boolean shouldCaptureThumbnail() {
-        // TODO(twellington): add more logic to this method that also takes into account other
-        // UI changes that should trigger a thumbnail capture.
-        return mNewTabPageLayout.shouldCaptureThumbnail();
+        return mNewTabPageLayout.shouldCaptureThumbnail() || mMediator.shouldCaptureThumbnail();
     }
 
     @Override
     public void captureThumbnail(Canvas canvas) {
         mNewTabPageLayout.onPreCaptureThumbnail();
         ViewUtils.captureBitmap(mRootView, canvas);
+        mMediator.onThumbnailCaptured();
     }
 
     /** @return The {@link Stream} that this class holds. */

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/FeedNewTabPageMediator.java

@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.feed;
 
 import android.content.res.Resources;
 
+import com.google.android.libraries.feed.api.stream.ContentChangedListener;
 import com.google.android.libraries.feed.api.stream.ScrollListener;
 import com.google.android.libraries.feed.api.stream.Stream;
 
@@ -27,8 +28,14 @@ class FeedNewTabPageMediator implements NewTabPageLayout.ScrollDelegate {
     private final PrefChangeRegistrar mPrefChangeRegistrar;
 
     private ScrollListener mStreamScrollListener;
+    private ContentChangedListener mStreamContentChangedListener;
     private SectionHeader mSectionHeader;
 
+    private boolean mStreamContentChanged;
+    private int mThumbnailWidth;
+    private int mThumbnailHeight;
+    private int mThumbnailScrollY;
+
     /**
      * @param feedNewTabPage The {@link FeedNewTabPage} that interacts with this class.
      */
@@ -44,7 +51,9 @@ class FeedNewTabPageMediator implements NewTabPageLayout.ScrollDelegate {
 
     /** Clears any dependencies. */
     void destroy() {
-        mCoordinator.getStream().removeScrollListener(mStreamScrollListener);
+        Stream stream = mCoordinator.getStream();
+        stream.removeScrollListener(mStreamScrollListener);
+        stream.removeOnContentChangedListener(mStreamContentChangedListener);
         mPrefChangeRegistrar.destroy();
     }
 
@@ -61,6 +70,7 @@ class FeedNewTabPageMediator implements NewTabPageLayout.ScrollDelegate {
                     mSnapScrollHelper.handleScroll();
                 });
 
+        Stream stream = mCoordinator.getStream();
         mStreamScrollListener = new ScrollListener() {
             @Override
             public void onScrollStateChanged(int state) {}
@@ -70,7 +80,10 @@ class FeedNewTabPageMediator implements NewTabPageLayout.ScrollDelegate {
                 mSnapScrollHelper.handleScroll();
             }
         };
-        mCoordinator.getStream().addScrollListener(mStreamScrollListener);
+        stream.addScrollListener(mStreamScrollListener);
+
+        mStreamContentChangedListener = () -> mStreamContentChanged = true;
+        stream.addOnContentChangedListener(mStreamContentChangedListener);
 
         Resources res = mCoordinator.getSectionHeaderView().getResources();
         mSectionHeader =
@@ -78,7 +91,7 @@ class FeedNewTabPageMediator implements NewTabPageLayout.ScrollDelegate {
                         PrefServiceBridge.getInstance().getBoolean(Pref.NTP_ARTICLES_LIST_VISIBLE),
                         this::onSectionHeaderToggled);
         mCoordinator.getSectionHeaderView().setHeader(mSectionHeader);
-        mCoordinator.getStream().setStreamContentVisibility(mSectionHeader.isExpanded());
+        stream.setStreamContentVisibility(mSectionHeader.isExpanded());
     }
 
     /** Update whether the section header should be expanded. */
@@ -101,6 +114,21 @@ class FeedNewTabPageMediator implements NewTabPageLayout.ScrollDelegate {
         mCoordinator.getSectionHeaderView().updateIconDrawable();
     }
 
+    /** Whether a new thumbnail should be captured. */
+    boolean shouldCaptureThumbnail() {
+        return mStreamContentChanged || mCoordinator.getView().getWidth() != mThumbnailWidth
+                || mCoordinator.getView().getHeight() != mThumbnailHeight
+                || getVerticalScrollOffset() != mThumbnailScrollY;
+    }
+
+    /** Reset all the properties for thumbnail capturing after a new thumbnail is captured. */
+    void onThumbnailCaptured() {
+        mThumbnailWidth = mCoordinator.getView().getWidth();
+        mThumbnailHeight = mCoordinator.getView().getHeight();
+        mThumbnailScrollY = getVerticalScrollOffset();
+        mStreamContentChanged = false;
+    }
+
     // ScrollDelegate interface.
 
     @Override