Add support for link repros and use it on net_perftests.

build/toolchain/win/BUILD.gn

 # 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.
 
 import("//build/config/clang/clang.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
@@ skipping 254 matching lines @@
       command = "$python_path $tool_wrapper_path link-wrapper $env False $link /nologo /OUT:$exename /PDB:$pdbname @$rspfile"
 
       if (is_official_build) {
         # On bots, the binary's PDB grow and eventually exceed 4G, causing the
         # link to fail. As there's no utility to keeping the PDB around
         # incrementally anyway in this config (because we're doing
         # non-incremental LTCG builds), delete it before linking.
         command = "cmd /c $python_path $tool_wrapper_path delete-file $pdbname && $command"
       }
 
+      if (linkrepro_root_dir != "") {
+        # Create the directory that will receive the link repro for this target
+        # if needed. Note that this will create one directory per link target
+        # even if this target doesn't generate a link repro. This is necessary
+        # because the linker doesn't generate the directory specified to the
+        # /LINKREPRO flag if it doesn't exist.
+        linkrepro_dir = "$linkrepro_root_dir\\{{target_output_name}}"
+        command = "cmd /c mkdir $linkrepro_dir && $command"
+      }
+
       default_output_extension = ".exe"
       default_output_dir = "{{root_out_dir}}"
       description = "LINK {{output}}"
       outputs = [
         exename,
       ]
       if (symbol_level != 0) {
         outputs += [ pdbname ]
       }
       runtime_outputs = outputs
@@ skipping 144 matching lines @@
   msvc_toolchain("winrt_x64") {
     environment = "environment.winrt_x64"
     cl = "${goma_prefix}\"${vc_bin_dir}/cl.exe\""
 
     toolchain_args = {
       is_clang = false
       current_cpu = "x64"
     }
   }
 }