Bug 1494712 - fix incorrect preprocessor define for aarch64 in atomicops.h; r=jld

ipc/chromium/src/base/atomicops.h

@@ -150,7 +150,7 @@ Atomic64 Release_Load(volatile const Atomic64* ptr);
 // Include our platform specific implementation.
 #if defined(OS_WIN) && defined(ARCH_CPU_X86_FAMILY)
 #include "base/atomicops_internals_x86_msvc.h"
-#elif defined(OS_WIN) && defined(ARCH_CPU_AARCH64_FAMILY)
+#elif defined(OS_WIN) && defined(ARCH_CPU_ARM64)
 // Works just fine, separate case in case we need to change things.
 #include "base/atomicops_internals_x86_msvc.h"
 #elif defined(OS_MACOSX) && defined(ARCH_CPU_X86_FAMILY)