Breakpad processor: Make PostfixEvaluator treat the MemoryRegion as const.

In order to be able to treat any MemoryRegion as const, the accessor
functions need to be declared this-const, which means annotations on
all the subclasses, etc. etc.

Since MinidumpMemoryRegion fills its memory_ member on demand, that
member needs to be marked 'mutable', but this is exactly the sort of
situation the 'mutable' keyword was intended for, so that seems all
right.

a=jimblandy, r=nealsid


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@509 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/processor/postfix_evaluator.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2006, Google Inc.
+// Copyright (c) 2010, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -90,7 +90,7 @@ class PostfixEvaluator {
   // (^) will not be supported.  |dictionary| may be NULL, but evaluation
   // will fail in that case unless set_dictionary is used before calling
   // Evaluate.
-  PostfixEvaluator(DictionaryType *dictionary, MemoryRegion *memory)
+  PostfixEvaluator(DictionaryType *dictionary, const MemoryRegion *memory)
       : dictionary_(dictionary), memory_(memory), stack_() {}
 
   // Evaluate the expression.  The results of execution will be stored
@@ -144,7 +144,7 @@ class PostfixEvaluator {
 
   // If non-NULL, the MemoryRegion used for dereference (^) operations.
   // If NULL, dereferencing is unsupported and will fail.  Weak pointer.
-  MemoryRegion *memory_;
+  const MemoryRegion *memory_;
 
   // The stack contains state information as execution progresses.  Values
   // are pushed on to it as the expression string is read and as operations