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..f6fe73cd7ea8ebcfc6493fc06f4d665132af595a
--- /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 {
+    public interface Delegate {
+        // Returns whether the update succeeded
+        boolean scrollContainerViewTo(int xPix, int yPix);
+        void scrollNativeTo(int xPix, int yPix);
+        int getContainerViewScrollXPix();
+        int getContainerViewScrollYPix();
+    }
+
+    final Delegate mDelegate;
+    boolean mIgnoreContainerViewScrollChanges;
+    int mNativeScrollXPix;
+    int mNativeScrollYPix;
+
+    public AwScrollOffsetManager(Delegate delegate) {
+        mDelegate = delegate;
+    }
+
+    public void scrollContainerViewTo(int xPix, int yPix) {
+        mNativeScrollXPix = xPix;
+        mNativeScrollYPix = yPix;
+
+        if (!mDelegate.scrollContainerViewTo(xPix, yPix)) {
+            scrollNativeTo(mDelegate.getContainerViewScrollXPix(),
+                    mDelegate.getContainerViewScrollYPix());
+        }
+    }
+
+    public void onContainerViewScrollChanged(int xPix, int yPix) {
+        scrollNativeTo(xPix, yPix);
+    }
+
+    private void scrollNativeTo(int xPix, int yPix) {
+        if (xPix == mNativeScrollXPix && yPix == mNativeScrollYPix)
+            return;
+
+        mNativeScrollXPix = xPix;
+        mNativeScrollYPix = yPix;
+
+        mDelegate.scrollNativeTo(xPix, yPix);
+    }
+}