Added unpacking step

chrome/installer/mac/app/Unpacker.h

Index: chrome/installer/mac/app/Unpacker.h
diff --git a/chrome/installer/mac/app/Unpacker.h b/chrome/installer/mac/app/Unpacker.h
new file mode 100644
index 0000000000000000000000000000000000000000..2ce987d668416c62f1b96bf7b77967dfafcf0586
--- /dev/null
+++ b/chrome/installer/mac/app/Unpacker.h
@@ -0,0 +1,28 @@
+// Copyright 2016 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 CHROME_INSTALLER_MAC_APP_UNPACKER_H_
+#define CHROME_INSTALLER_MAC_APP_UNPACKER_H_
+
+#import <Foundation/Foundation.h>
+
+// TODO: make paths not depend on location of executable
+#define PATH_FROM_EXECUTABLE(x)                                          \
+  [[[[NSBundle mainBundle] bundlePath] stringByAppendingPathComponent:x] \
+      stringByResolvingSymlinksInPath]
+
+@protocol UnpackDelegate
+- (void)onUnpackSuccess;
+@end
+
+@interface Unpacker : NSObject
+
+@property(nonatomic, assign) id<UnpackDelegate> delegate;
+
+- (void)mountDMG;
+- (void)unmountDMG;
+
+@end
+
+#endif  // CHROME_INSTALLER_MAC_APP_UNPACKER_H_