base/allocator: Enable PA-Everywhere on Windows (static release build)

To sheriffs: This patch may cause test failures on water falls.
Please revert this patch in that case.

This patch enables PartitionAlloc-Everywhere (aka PartitionAlloc
as malloc) on Windows static release builds.

Perf results:
https://docs.google.com/document/d/16LuLl6wVlJ4w8rKQB7N9_emYiA1NJUm77HaApoFA2Jg/edit?usp=sharing

Bug: 1121427
Change-Id: Ib0559095a305ba1c02b43669eedd771d6db8f667
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2543884Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Bartek Nowierski <bartekn@chromium.org>
Reviewed-by: Benoit L <lizeb@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828615}

base/allocator/allocator.gni

@@ -16,20 +16,20 @@ if ((is_linux || is_chromeos || is_android || is_apple ||
   _default_use_allocator_shim = false
 }
 
-# Temporarily disable tcmalloc on arm64 linux to get rid of compilation errors.
-if (is_android || is_apple || is_asan || is_lsan || is_tsan || is_msan ||
-    is_win || is_fuchsia ||
-    ((is_linux || is_chromeos) && target_cpu == "arm64") ||
-    (is_cast_audio_only && target_cpu == "arm")) {
+if (_default_use_allocator_shim && is_win) {
+  _default_allocator = "partition"
+} else if (is_android || is_apple || is_asan || is_lsan || is_tsan || is_msan ||
+           is_win || is_fuchsia ||
+           ((is_linux || is_chromeos) && target_cpu == "arm64") ||
+           (is_cast_audio_only && target_cpu == "arm")) {
+  # Temporarily disable tcmalloc on arm64 linux to get rid of compilation
+  # errors.
   _default_allocator = "none"
 } else {
   _default_allocator = "tcmalloc"
 }
 
 declare_args() {
-  # Don't ship this configuration, not ready yet.
-  assert(_default_allocator != "partition")
-
   # Memory allocator to use. Set to "none" to use default allocator.
   use_allocator = _default_allocator