Modify allocator_shim to support _aligned_alloc(), _aligned_free().

base/allocator/win_allocator.cc

Index: base/allocator/win_allocator.cc
diff --git a/base/allocator/win_allocator.cc b/base/allocator/win_allocator.cc
index 8ae653a690ed033b5e708e7021f98998082f0ca1..5367509ba4f3abc855ead1b428231581ca16506d 100644
--- a/base/allocator/win_allocator.cc
+++ b/base/allocator/win_allocator.cc
@@ -47,4 +47,26 @@ size_t win_heap_msize(void* ptr) {
   return HeapSize(win_heap, 0, ptr);
 }
 
+void* win_heap_memalign(size_t alignment, size_t size) {
+  // Reserve enough space to ensure we can align and set aligned_ptr[-1] to the
+  // original allocation for use with win_heap_memalign_free() later.
+  size_t allocation_size = size + (alignment - 1) + sizeof(void*);
+
+  // Check for overflow.  Alignment and size are checked in allocator_shim.
+  DCHECK_LT(size, allocation_size);
+  DCHECK_LT(alignment, allocation_size);
+
+  void* ptr = win_heap_malloc(allocation_size);
+  char* aligned_ptr = static_cast<char*>(ptr) + sizeof(void*);
+  aligned_ptr +=
+      alignment - reinterpret_cast<uintptr_t>(aligned_ptr) & (alignment - 1);
+
+  reinterpret_cast<void**>(aligned_ptr)[-1] = ptr;
+  return aligned_ptr;
+}
+
+void win_heap_memalign_free(void* ptr) {
+  win_heap_free(static_cast<void**>(ptr)[-1]);
+}
+
 }  // extern "C"