Add another missing #include.

Change-Id: I5a34f78e0387d249185a9f3e24c7fd77a40c5a9b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/12841
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>

src/dawn_native/ResourceHeapAllocator.h

@@ -18,6 +18,8 @@
 #include "dawn_native/Error.h"
 #include "dawn_native/ResourceHeap.h"
 
+#include <memory>
+
 namespace dawn_native {
 
     // Interface for backend allocators that create memory heaps resoruces can be suballocated in.