Hookup android_webview scroll offset delegation to Java side.

android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java

Index: android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java b/android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java
new file mode 100644
index 0000000000000000000000000000000000000000..2e3955cab43d4a9d118bbd4e1f6c349455ff9f52
--- /dev/null
+++ b/android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java
@@ -0,0 +1,50 @@
+// Copyright 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.android_webview;
+
+import org.chromium.base.CalledByNative;
+
+class AwScrollOffsetManager {
+    // The unit of all the values in this delegate are physical pixels
+    public interface Delegate {
+        // Returns whether the update succeeded
+        boolean scrollContainerViewTo(int x, int y);
+        void scrollNativeTo(int x, int y);
+        int getContainerViewScrollX();
+        int getContainerViewScrollY();
+    }
+
+    final Delegate mDelegate;
+    int mNativeScrollX;
+    int mNativeScrollY;
+
+    public AwScrollOffsetManager(Delegate delegate) {
+        mDelegate = delegate;
+    }
+
+    public void scrollContainerViewTo(int x, int y) {
+        mNativeScrollX = x;
+        mNativeScrollY = y;
+
+        if (!mDelegate.scrollContainerViewTo(x, y)) {
+            scrollNativeTo(mDelegate.getContainerViewScrollX(),
+                    mDelegate.getContainerViewScrollY());
+        }
+    }
+
+    public void onContainerViewScrollChanged(int x, int y) {
+        scrollNativeTo(x, y);
+    }
+
+    private void scrollNativeTo(int x, int y) {
+        if (x == mNativeScrollX && y == mNativeScrollY)
+            return;
+
+        mNativeScrollX = x;
+        mNativeScrollY = y;
+
+        mDelegate.scrollNativeTo(x, y);
+    }
+}