[wasm] Disable trap handlers also in d8.

This feature is turned off in flag-definitions but reenabled in a non-standard
way in d8. Given that the situations in which the trap handler are disabled are
more limited now due to integration problems, disabling this feature for now, since
we lack enough coverage to have confidence to turn it on by default.

We should probably introduce a proper test variant for this feature so that it
can be handled in a more standard way.

R=eholk@chromium.org
CC=​mlippautz@chromium.org,hablich@chromium.org,mstarzinger@chromium.org

Bug: 
Change-Id: Ic2e13181036ace8802736be847ae16ff889e3cea
Reviewed-on: https://chromium-review.googlesource.com/723221
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Eric Holk <eholk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48646}

src/d8.cc

@@ -2805,16 +2805,6 @@ bool Shell::SetOptions(int argc, char* argv[]) {
     }
   }
 
-// On x64 Linux we want to enable the Wasm trap handler by default. Setting
-// the flag here allows the command line argument to still override it.
-//
-// Currently we leave the default unchanged for sanitizers.
-//
-// TODO(eholk): enable trap handlers on sanitizers once issues are resolved.
-#if !defined(V8_USE_ADDRESS_SANITIZER) && !defined(LEAK_SANITIZER) && \
-    !defined(THREAD_SANITIZER) && V8_OS_LINUX && V8_TARGET_ARCH_X64
-  SetFlagsFromString("--wasm-trap-handler");
-#endif
   v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
 
   // Set up isolated source groups.