Work on GN iOS build.

tools/gn/args.h

 // Copyright (c) 2013 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 TOOLS_GN_ARGS_H_
 #define TOOLS_GN_ARGS_H_
 
 #include "base/basictypes.h"
 #include "base/containers/hash_tables.h"
 #include "base/synchronization/lock.h"
@@ skipping 13 matching lines @@
  public:
   Args();
   Args(const Args& other);
   ~Args();
 
   // Specifies overrides of the build arguments. These are normally specified
   // on the command line.
   void AddArgOverride(const char* name, const Value& value);
   void AddArgOverrides(const Scope::KeyValueMap& overrides);
 
+  // Returns the value corresponding to the given argument name, or NULL if no
+  // argument is set.
+  const Value* GetArgOverride(const char* name) const;
+
   // Sets up the root scope for a toolchain. This applies the default system
   // flags, then any overrides stored in this object, then applies any
   // toolchain overrides specified in the argument.
   void SetupRootScope(Scope* dest,
                       const Scope::KeyValueMap& toolchain_overrides) const;
 
   // Sets up the given scope with arguments passed in.
   //
   // If the values specified in the args are not already set, the values in
   // the args list will be used (which are assumed to be the defaults), but
@@ skipping 37 matching lines @@
   mutable Scope::KeyValueMap all_overrides_;
 
   // Tracks all variables declared in any buildfile. This is so we can see if
   // the user set variables on the command line that are not used anywhere.
   mutable Scope::KeyValueMap declared_arguments_;
 
   Args& operator=(const Args& other);  // Disallow assignment.
 };
 
 #endif  // TOOLS_GN_ARGS_H_