Move setValue operation into a separate JsDeclarativeVariable interface

plugins/org.chromium.sdk/src/org/chromium/sdk/JsDeclarativeVariable.java

+// Copyright (c) 2013 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.sdk;
+
+/**
+ * A variable from JavaScript declarative scope. This variable is backed by a property
+ * of any object, instead it is a variable that has been explicitly declared in program,
+ * for example with 'var' keyword.
+ * <p>This variable explicitly supports mutation operation.
+ * @see {@link JsScope.Declarative}
+ */
+public interface JsDeclarativeVariable extends JsVariable {
+  /**
+   * @return whether it is possible to modify this variable
+   */
+  boolean isMutable();
+
+  /**
+   * Sets a new value for this variable.
+   *
+   * @param newValue to set
+   * @param callback to report the operation result to
+   * @param syncCallback to report the end of any processing
+   * @see #isMutable()
+   * @throws UnsupportedOperationException if this variable is not mutable
+   */
+  RelayOk setValue(JsValue newValue, SetValueCallback callback, SyncCallback syncCallback)
+      throws UnsupportedOperationException;
+
+  /**
+   * A callback to use while setting a variable value.
+   */
+  interface SetValueCallback {
+    /**
+     * Variable is successfully updated. New value is available in {@link JsVariable#getValue()}.
+     */
+    void success();
+
+    /**
+     * Variable hasn't been updated for unknown reason.
+     */
+    void failure(Exception cause);
+  }
+}