MdeModulePkg: Variable: Update PCR[7] measure for new TCG spec

Measure DBT into PCR[7] when it is updated between initial measure and
ExitBootService. Measure "SecureBoot" change after PK update.
Spec version : TCG PC Client PFP 00.37. http://www.trustedcomputinggroup.org/wp-content/uploads/PC-ClientSpecific_Platform_Profile_for_TPM_2p0_Systems_v21.pdf

Cc: Star Zeng <star.zeng@intel.com>
Cc: Yao Jiewen <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Chao Zhang <chao.b.zhang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Yao Jiewen <jiewen.yao@intel.com>

MdeModulePkg/Universal/Variable/RuntimeDxe/VariableDxe.c

@@ -3,7 +3,7 @@
   and volatile storage space and install variable architecture protocol.
 
 Copyright (C) 2013, Red Hat, Inc.
-Copyright (c) 2006 - 2015, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
 (C) Copyright 2015 Hewlett Packard Enterprise Development LP<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
@@ -31,6 +31,17 @@ EDKII_VAR_CHECK_PROTOCOL            mVarCheck                  = { VarCheckRegis
                                                                     VarCheckVariablePropertySet,
                                                                     VarCheckVariablePropertyGet };
 
+/**
+  Some Secure Boot Policy Variable may update following other variable changes(SecureBoot follows PK change, etc).
+  Record their initial State when variable write service is ready.
+
+**/
+VOID
+EFIAPI
+RecordSecureBootPolicyVarData(
+  VOID
+  );
+
 /**
   Return TRUE if ExitBootServices () has been called.
 
@@ -414,6 +425,12 @@ FtwNotificationEvent (
     DEBUG ((DEBUG_ERROR, "Variable write service initialization failed. Status = %r\n", Status));
   }
 
+  //
+  // Some Secure Boot Policy Var (SecureBoot, etc) updates following other
+  // Secure Boot Policy Variable change. Record their initial value.
+  //
+  RecordSecureBootPolicyVarData();
+
   //
   // Install the Variable Write Architectural protocol.
   //