reported upstream: https://issues.chromium.org/issues/330361615

The forward header includes the declaration of deallocate(), but not the
definition. Since the definition is in a header (and presumably it gets
inlined by the compiler), the definition doesn't actually end up in an
object file unless the non-forward header gets included. Not having the
definition makes the linker sad.

--- a/base/allocator/partition_allocator/src/partition_alloc/starscan/stats_collector.h
+++ b/base/allocator/partition_allocator/src/partition_alloc/starscan/stats_collector.h
@@ -14,7 +14,7 @@
 #include <unordered_map>
 #include <utility>
 
-#include "partition_alloc/internal_allocator_forward.h"
+#include "partition_alloc/internal_allocator.h"
 #include "partition_alloc/partition_alloc_base/threading/platform_thread.h"
 #include "partition_alloc/partition_alloc_base/time/time.h"
 #include "partition_alloc/partition_alloc_check.h"