[Fuchsia] Use ZX_VMO_NON_RESIZABLE for zx_vmo_create()

By default zx_vmo_create() creates resizable VMOs, which may be
hazardous in some cases. It's safer to use ZX_VMO_NON_RESIZABLE unless
VMO needs to be resizable. It doesn't make much difference in
OS::Allocate() because it drops the VMO handle immediately after
mapping it, still it's better to use ZX_VMO_NON_RESIZABLE for
consistency.

Change-Id: I688ee44b08042a9df7e3fae0b1b3298271b53b1c
Reviewed-on: https://chromium-review.googlesource.com/c/1277605Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56788}

src/base/platform/platform-fuchsia.cc

@@ -49,7 +49,7 @@ void* OS::Allocate(void* address, size_t size, size_t alignment,
   size_t request_size = size + (alignment - page_size);
 
   zx_handle_t vmo;
-  if (zx_vmo_create(request_size, 0, &vmo) != ZX_OK) {
+  if (zx_vmo_create(request_size, ZX_VMO_NON_RESIZABLE, &vmo) != ZX_OK) {
     return nullptr;
   }
   static const char kVirtualMemoryName[] = "v8-virtualmem";