Remove obsolete "link_pool" code from GN's ninja writer.

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/files/file_util.h"
 #include "base/strings/stringize_macros.h"
@@ skipping 92 matching lines @@
   } else if (tool->depsformat() == Tool::DEPS_MSVC) {
     // MSVC deps don't have a depfile.
     out_ << kIndent << "deps = msvc" << std::endl;
   }
 
   // Use pool is specified.
   if (tool->pool().ptr) {
     std::string pool_name =
         tool->pool().ptr->GetNinjaName(settings_->default_toolchain_label());
     out_ << kIndent << "pool = " << pool_name << std::endl;
-  } else if (type == Toolchain::TYPE_SOLINK ||
-      type == Toolchain::TYPE_SOLINK_MODULE ||
-      type == Toolchain::TYPE_LINK) {
-    // The link pool applies to linker tools. Don't count TYPE_ALINK since
-    // static libraries are not generally intensive to write.
-    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;
 }