Plumb an overscroll callback form the compositor to the Android UI thread.

content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java

Index: content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
index 0420735db44d1da797856e2472589ce9239337a9..3d0adc411164daddd4f6769b97f557011e3671c7 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
@@ -157,6 +157,14 @@ public class ContentViewCore implements MotionEventDelegate, NavigationClient {
          * @see View#awakenScrollBars(int, boolean)
          */
         boolean super_awakenScrollBars(int startDelay, boolean invalidate);
+
+        /**
+         * Called when the user tries to scroll more than it is possible.
+         *
+         * @param deltaX "left over" horizontal scroll offset.
+         * @param deltaX "left over" vertical scroll offset.
+         */
+        void onOverScroll(int deltaX, int deltaY);
     }
 
     /**
@@ -1969,6 +1977,14 @@ public class ContentViewCore implements MotionEventDelegate, NavigationClient {
 
     @SuppressWarnings("unused")
     @CalledByNative
+    private void updateUnusedScrollOffset(int x, int y) {
+        if (x != 0 && y != 0) {
+            mContainerViewInternals.onOverScroll(x, y);
+        }
+    }
+
+    @SuppressWarnings("unused")
+    @CalledByNative
     private void imeUpdateAdapter(int nativeImeAdapterAndroid, int textInputType,
             String text, int selectionStart, int selectionEnd,
             int compositionStart, int compositionEnd, boolean showImeIfNeeded) {