Plumb smooth scrolling in Chromium compositor

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 974f69353e715413a06e07cd2a46528d41c74b49..fec7756f42d916fe7ba13dfac780588306f3039f 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
@@ -1244,8 +1244,7 @@ public class ContentViewCore implements
     }
 
     public boolean isScrollInProgress() {
-        return mTouchScrollInProgress || mPotentiallyActiveFlingCount > 0
-                || getContentViewClient().isExternalScrollActive();
+        return mTouchScrollInProgress || mPotentiallyActiveFlingCount > 0;
     }
 
     @SuppressWarnings("unused")
@@ -1354,6 +1353,13 @@ public class ContentViewCore implements
         nativeFlingStart(mNativeContentViewCore, timeMs, 0, 0, velocityX, velocityY, true);
     }
 
+    public void smoothScroll(long timeMs, int startX, int startY, int dx, int dy, long durationMs) {
+        if (mNativeContentViewCore == 0) return;
+        nativeFlingCancel(mNativeContentViewCore, timeMs);
+        nativeScrollBegin(mNativeContentViewCore, timeMs, startX, startY, -dx, -dy, true);
+        nativeSmoothScrollStart(mNativeContentViewCore, timeMs, startX, startY, dx, dy, durationMs);
+    }
+
     /**
      * Cancel any fling gestures active.
      * @param timeMs Current time (in milliseconds).
@@ -1395,9 +1401,6 @@ public class ContentViewCore implements
                             computeVerticalScrollOffset(),
                             computeVerticalScrollExtent());
                     break;
-                case GestureEventType.FLING_CANCEL:
-                    listener.onFlingCancelGesture();
-                    break;
                 case GestureEventType.SCROLL_START:
                     listener.onScrollStarted(
                             computeVerticalScrollOffset(),
@@ -3247,6 +3250,9 @@ public class ContentViewCore implements
 
     private native void nativeFlingCancel(long nativeContentViewCoreImpl, long timeMs);
 
+    private native void nativeSmoothScrollStart(long nativeContentViewCoreImpl, long timeMs,
+            float startX, float startY, float dx, float dy, long durationMs);
+
     private native void nativeSingleTap(
             long nativeContentViewCoreImpl, long timeMs, float x, float y);