Add support for user defined "pool" to GN.

tools/gn/builder_record.cc

 // 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.
 
 #include "tools/gn/builder_record.h"
 
 #include "tools/gn/item.h"
 
 BuilderRecord::BuilderRecord(ItemType type, const Label& label)
     : type_(type),
       label_(label),
       originally_referenced_from_(nullptr),
       should_generate_(false),
       resolved_(false) {
 }
 
 BuilderRecord::~BuilderRecord() {
 }
 
 // static
 const char* BuilderRecord::GetNameForType(ItemType type) {
   switch (type) {
     case ITEM_TARGET:
       return "target";
     case ITEM_CONFIG:
       return "config";
     case ITEM_TOOLCHAIN:
       return "toolchain";
+    case ITEM_POOL:
+      return "pool";
     case ITEM_UNKNOWN:
     default:
       return "unknown";
   }
 }
 
 // static
 bool BuilderRecord::IsItemOfType(const Item* item, ItemType type) {
   switch (type) {
     case ITEM_TARGET:
       return !!item->AsTarget();
     case ITEM_CONFIG:
       return !!item->AsConfig();
     case ITEM_TOOLCHAIN:
       return !!item->AsToolchain();
+    case ITEM_POOL:
+      return !!item->AsPool();
     case ITEM_UNKNOWN:
     default:
       return false;
   }
 }
 
 // static
 BuilderRecord::ItemType BuilderRecord::TypeOfItem(const Item* item) {
   if (item->AsTarget())
     return ITEM_TARGET;
   if (item->AsConfig())
     return ITEM_CONFIG;
   if (item->AsToolchain())
     return ITEM_TOOLCHAIN;
+  if (item->AsPool())
+    return ITEM_POOL;
 
   NOTREACHED();
   return ITEM_UNKNOWN;
 }
 
 void BuilderRecord::AddDep(BuilderRecord* record) {
   all_deps_.insert(record);
   if (!record->resolved()) {
     unresolved_deps_.insert(record);
     record->waiting_on_resolution_.insert(this);
   }
 }