allocator/Windows: delete the old non-unified allocator-shim

build/config/allocator.gni

 # Copyright 2014 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/sanitizers/sanitizers.gni")
 
 # Temporarily disable tcmalloc on arm64 linux to get rid of compilation errors.
 if (is_android || current_cpu == "mipsel" || is_mac || is_ios || is_asan ||
     is_lsan || is_tsan || is_msan || is_win || is_syzyasan || is_fuchsia ||
     (is_linux && target_cpu == "arm64")) {
@@ skipping 10 matching lines @@
     !is_tsan && !is_msan) {
   _default_use_allocator_shim = true
 } else {
   _default_use_allocator_shim = false
 }
 
 declare_args() {
   # Memory allocator to use. Set to "none" to use default allocator.
   use_allocator = _default_allocator
 
-  # TODO(primiano): this should just become the default without having a flag,
-  # but we need to get there first. http://crbug.com/550886 .
   # Causes all the allocations to be routed via allocator_shim.cc.
   use_allocator_shim = _default_use_allocator_shim
 }
 
 if (is_nacl) {
   # Turn off the build flag for NaCL builds to minimize confusion, as NaCL
   # doesn't support the heap shim.
   use_allocator_shim = false
 }
 
 assert(use_allocator == "none" || use_allocator == "tcmalloc")
 
 assert(!is_win || use_allocator == "none", "Tcmalloc doesn't work on Windows.")
 assert(!is_mac || use_allocator == "none", "Tcmalloc doesn't work on macOS.")
 
 assert(
     !use_allocator_shim || is_linux || is_android || is_win || is_mac,
     "use_allocator_shim is supported only on Linux, Android, Windows and macOS targets")
 
 if (is_win && use_allocator_shim) {
   assert(!is_component_build,
          "The allocator shim doesn't work for the component build on Windows.")
 }