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

base/allocator/README.md

 This document describes how malloc / new calls are routed in the various Chrome
 platforms.
 
 Bare in mind that the chromium codebase does not always just use `malloc()`.
 Some examples:
  - Large parts of the renderer (Blink) use two home-brewed allocators,
    PartitionAlloc and BlinkGC (Oilpan).
  - Some subsystems, such as the V8 JavaScript engine, handle memory management
    autonomously.
  - Various parts of the codebase use abstractions such as `SharedMemory` or
    `DiscardableMemory` which, similarly to the above, have their own page-level
    memory management.
 
 Background
 ----------
 The `allocator` target defines at compile-time the platform-specific choice of
 the allocator and extra-hooks which services calls to malloc/new. The relevant
-build-time flags involved are `use_allocator` and `win_use_allocator_shim`.
+build-time flags involved are `use_allocator` and `use_allocator_shim`.
 
 The default choices are as follows:
 
 **Windows**  
 `use_allocator: winheap`, the default Windows heap.
 Additionally, `static_library` (i.e. non-component) builds have a shim
-layer wrapping malloc/new, which is controlled by `win_use_allocator_shim`.  
+layer wrapping malloc/new, which is controlled by `use_allocator_shim`.  
 The shim layer provides extra security features, such as preventing large
 allocations that can hit signed vs. unsigned bugs in third_party code.
 
 **Linux Desktop / CrOS**  
 `use_allocator: tcmalloc`, a forked copy of tcmalloc which resides in
 `third_party/tcmalloc/chromium`. Setting `use_allocator: none` causes the build
 to fall back to the system (Glibc) symbols.
 
 **Android**  
 `use_allocator: none`, always use the allocator symbols coming from Android's
@@ skipping 152 matching lines @@
 Related links
 -------------
 - [Unified allocator shim doc - Feb 2016][url-allocator-shim]
 - [Allocator cleanup doc - Jan 2016][url-allocator-cleanup]
 - [Proposal to use PartitionAlloc as default allocator](https://crbug.com/339604)
 - [Memory-Infra: Tools to profile memory usage in Chrome](/docs/memory-infra/README.md)
 
 [url-allocator-cleanup]: https://docs.google.com/document/d/1V77Kgp_4tfaaWPEZVxNevoD02wXiatnAv7Ssgr0hmjg/edit?usp=sharing
 [url-memory-infra-heap-profiler]: /docs/memory-infra/heap_profiler.md
 [url-allocator-shim]: https://docs.google.com/document/d/1yKlO1AO4XjpDad9rjcBOI15EKdAGsuGO_IeZy0g0kxo/edit?usp=sharing