Abstract WebContentsObserver from Autofill shared code

components/autofill/browser/autofill_driver.h

+// Copyright 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.
+
+#ifndef COMPONENTS_AUTOFILL_BROWSER_AUTOFILL_DRIVER_H_
+#define COMPONENTS_AUTOFILL_BROWSER_AUTOFILL_DRIVER_H_
+
+namespace content {
+class WebContents;
+}
+
+namespace autofill {
+
+// Interface that provides access to the driver-level context in which Autofill
+// is operating. A concrete implementation must be provided by the driver.
+class AutofillDriver {
+ public:
+  virtual ~AutofillDriver() {}
+
+  // TODO(blundell): Remove this method once shared code no longer needs to
+  // know about WebContents.
+  virtual content::WebContents* GetWebContents() = 0;
+};
+
+}  // namespace autofill
+
+#endif  // COMPONENTS_AUTOFILL_BROWSER_AUTOFILL_DRIVER_H_