Hook up link pools in GN.

tools/gn/ninja_toolchain_writer.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/ninja_toolchain_writer.h"
 
 #include <fstream>
 
 #include "base/file_util.h"
 #include "base/strings/stringize_macros.h"
@@ skipping 87 matching lines @@
     // GCC-style deps require a depfile.
     if (!tool->depfile().empty()) {
       WriteRulePattern("depfile", tool->depfile(), options);
       out_ << kIndent << "deps = gcc" << std::endl;
     }
   } else if (tool->depsformat() == Tool::DEPS_MSVC) {
     // MSVC deps don't have a depfile.
     out_ << kIndent << "deps = msvc" << std::endl;
   }
 
-  if (!tool->pool().empty())
-    out_ << kIndent << "pool = " << tool->pool() << std::endl;
+  // The link pool applies to linker tools. Don't count TYPE_ALINK since
+  // static libraries are not generally intensive to write.
+  if (type == Toolchain::TYPE_SOLINK || type == Toolchain::TYPE_LINK)
+    out_ << kIndent << "pool = link_pool\n";
+
   if (tool->restat())
     out_ << kIndent << "restat = 1" << std::endl;
 }
 
 void NinjaToolchainWriter::WriteRulePattern(const char* name,
                                             const SubstitutionPattern& pattern,
                                             const EscapeOptions& options) {
   if (pattern.empty())
     return;
   out_ << kIndent << name << " = ";
   SubstitutionWriter::WriteWithNinjaVariables(pattern, options, out_);
   out_ << std::endl;
 }
 
 void NinjaToolchainWriter::WriteSubninjas() {
   // Write subninja commands for each generated target.
   for (size_t i = 0; i < targets_.size(); i++) {
     OutputFile ninja_file(targets_[i]->settings()->build_settings(),
                           GetNinjaFileForTarget(targets_[i]));
     out_ << "subninja ";
     path_output_.WriteFile(out_, ninja_file);
     out_ << std::endl;
   }
   out_ << std::endl;
 }