NTP, peeking card and heading hiding constraints

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/CardViewHolder.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/CardViewHolder.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/CardViewHolder.java
index c5a2ef4e8e4ba590433cc31f6878ceba029fb3b4..f45eb14d1c7139e11ee8df8297b226937886bb35 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/CardViewHolder.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/CardViewHolder.java
@@ -127,11 +127,23 @@ public class CardViewHolder extends NewTabPageViewHolder {
                 viewportHeight - mMaxPeekPadding - itemView.getTop(), 0, mMaxPeekPadding));
     }
 
-    /** Returns whether the card is currently peeking. */
+    /**
+     * @return Whether the card is peeking.
+     */
     public boolean isPeeking() {
         return mPeekPadding < mMaxPeekPadding;
     }
 
+    /**
+     * @return Whether the card can peek.
+     */
+    public boolean canPeek() {
+        // Only allow the card to peek if the user has not scrolled on the page beyond the
+        // |mMaxPeekPadding| height. There will only ever be one peeking card on the page and only
+        // when there is enough space to show the peeking card on the first screen at the bottom.
+        return mRecyclerView.computeVerticalScrollOffset() <= itemView.getHeight();
+    }
+
     @Override
     public void updateViewStateForDismiss(float dX) {
         float input = Math.abs(dX) / itemView.getMeasuredWidth();
@@ -148,7 +160,7 @@ public class CardViewHolder extends NewTabPageViewHolder {
     private void setPeekingStateForPadding(int padding) {
         // TODO(mcwilliams): Change the 'padding' value to a percentage of what the transition
         // should be which can be used for alpha and bleed.
-        mPeekPadding = padding;
+        mPeekPadding = canPeek() ? padding : mMaxPeekPadding;
 
         // Modify the padding so as the margin increases, the padding decreases, keeping the card's
         // contents in the same position. The top and bottom remain the same.