Refactor StringPiece hash.

tools/gn/scope.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_SCOPE_H_
 #define TOOLS_GN_SCOPE_H_
 
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 22 matching lines @@
 // values resursively down the stack until a match is found or there are no
 // more containing scopes.
 //
 // A containing scope can be const or non-const. The const containing scope is
 // used primarily to refer to the master build config which is shared across
 // many invocations. A const containing scope, however, prevents us from
 // marking variables "used" which prevents us from issuing errors on unused
 // variables. So you should use a non-const containing scope whenever possible.
 class Scope {
  public:
-  typedef base::hash_map<base::StringPiece, Value> KeyValueMap;
+  typedef base::hash_map<base::StringPiece, Value, base::StringPieceHash>
+      KeyValueMap;
   // Holds an owning list of Items.
   typedef ScopedVector<Item> ItemVector;
 
   // Allows code to provide values for built-in variables. This class will
   // automatically register itself on construction and deregister itself on
   // destruction.
   class ProgrammaticProvider {
    public:
     explicit ProgrammaticProvider(Scope* scope) : scope_(scope) {
       scope_->AddProvider(this);
@@ skipping 268 matching lines @@
   // change things (especially marking unused vars).
   const Scope* const_containing_;
   Scope* mutable_containing_;
 
   const Settings* settings_;
 
   // Bits set for different modes. See the flag definitions in the .cc file
   // for more.
   unsigned mode_flags_;
 
-  typedef base::hash_map<base::StringPiece, Record> RecordMap;
+  typedef base::hash_map<base::StringPiece, Record, base::StringPieceHash>
+      RecordMap;
   RecordMap values_;
 
   // Owning pointers. Note that this can't use string pieces since the names
   // are constructed from Values which might be deallocated before this goes
   // out of scope.
   typedef base::hash_map<std::string, Scope*> NamedScopeMap;
   NamedScopeMap target_defaults_;
 
   // Null indicates not set and that we should fallback to the containing
   // scope's filter.
@@ skipping 11 matching lines @@
 
   typedef std::set<ProgrammaticProvider*> ProviderSet;
   ProviderSet programmatic_providers_;
 
   SourceDir source_dir_;
 
   DISALLOW_COPY_AND_ASSIGN(Scope);
 };
 
 #endif  // TOOLS_GN_SCOPE_H_