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..f73d16b6ddb83a8912ba54f0955fad2adf9ade56
--- /dev/null
+++ b/chrome/installer/mac/app/Unpacker.h
@@ -0,0 +1,30 @@
+// 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>
+
+@class Unpacker;
+@protocol UnpackDelegate<NSObject>
+- (void)unpacker:(Unpacker*)unpacker onMountSuccess:(NSString*)tempAppPath;
+- (void)unpacker:(Unpacker*)unpacker onMountFailure:(NSError*)error;
+- (void)unpacker:(Unpacker*)unpacker onUnmountSuccess:(NSString*)mountpath;
+- (void)unpacker:(Unpacker*)unpacker onUnmountFailure:(NSError*)error;
+@end
+
+@interface Unpacker : NSObject
+
+@property(nonatomic, assign) id<UnpackDelegate> delegate;
+@property(nonatomic, copy) NSString* appPath;
+
+// Mount a disk image at |fileURL|.
+- (void)mountDMGFromURL:(NSURL*)fileURL;
+// Unmount that same disk image.
+- (void)unmountDMG;
+
+@end
+
+#endif  // CHROME_INSTALLER_MAC_APP_UNPACKER_H_