[heap] Turn on --write-protect-code-memory.

Bug: chromium:774108
Change-Id: Ifcf9939f29c9a3dc14ed686dc14608860ff32678
Reviewed-on: https://chromium-review.googlesource.com/950902Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51766}

src/flag-definitions.h

@@ -523,7 +523,7 @@ DEFINE_DEBUG_BOOL(wasm_trace_native_heap, false,
                   "trace wasm native heap events")
 DEFINE_BOOL(wasm_jit_to_native, true,
             "JIT wasm code to native (not JS GC) memory")
-DEFINE_BOOL(wasm_write_protect_code_memory, false,
+DEFINE_BOOL(wasm_write_protect_code_memory, true,
             "write protect code memory on the wasm native heap")
 DEFINE_IMPLICATION(future, wasm_jit_to_native)
 DEFINE_BOOL(wasm_trace_serialization, false,