ShellPkg: Make the USB mouse behavior in 'edit' consistent with 'hexedit'.

1. Make the USB mouse cursor move smoothly in 'edit'.
2. Make the USB mouse can drag and select text in 'edit'.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>

ShellPkg/Library/UefiShellDebug1CommandsLib/Edit/FileBuffer.h

@@ -1,7 +1,7 @@
 /** @file
   Declares filebuffer interface functions.
 
-  Copyright (c) 2005 - 2011, Intel Corporation. All rights reserved. <BR>
+  Copyright (c) 2005 - 2016, Intel Corporation. All rights reserved. <BR>
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at
@@ -260,4 +260,14 @@ FileBufferSetModified (
   VOID
   );
 
+/**
+  Get the size of the open buffer.
+
+  @retval The size in bytes.
+**/
+UINTN
+FileBufferGetTotalSize (
+  VOID
+  );
+
 #endif