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

media/base/BUILD.gn

Index: media/base/BUILD.gn
diff --git a/media/base/BUILD.gn b/media/base/BUILD.gn
index ffd1027a251e47c2800f9b2cb8083c62654d1ea7..ee1193fe9fc4cf8ff64a5b0f21d3ca969fb2f516 100644
--- a/media/base/BUILD.gn
+++ b/media/base/BUILD.gn
@@ -16,8 +16,6 @@ if (is_android) {
 
 config("base_config") {
   configs = [
-    # This target uses the ALLOCATOR_SHIM define.
-    "//base/allocator:allocator_shim_define",
     "//build/config:precompiled_headers",
     "//build/config/compiler:no_size_t_to_int_warning",
     "//media:media_config",
@@ -281,6 +279,8 @@ target(link_target_type, "base") {
     "//ui/gfx:color_space",
   ]
   deps = [
+    # For BUILDFLAG(USE_ALLOCATOR_SHIM).
+    "//base/allocator:features",
     "//base/third_party/dynamic_annotations:dynamic_annotations",
     "//gpu",
     "//media:media_features",