Revert of Remove wasm compile time option and enable wasm behind a runtime flag.

src/bootstrapper.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
 #include "src/extensions/free-buffer-extension.h"
 #include "src/extensions/gc-extension.h"
 #include "src/extensions/statistics-extension.h"
 #include "src/extensions/trigger-failure-extension.h"
 #include "src/heap/heap.h"
 #include "src/isolate-inl.h"
 #include "src/snapshot/natives.h"
 #include "src/snapshot/snapshot.h"
+#include "third_party/fdlibm/fdlibm.h"
+
+#if defined(V8_WASM)
 #include "src/wasm/wasm-js.h"
+#endif
 
 namespace v8 {
 namespace internal {
 
 Bootstrapper::Bootstrapper(Isolate* isolate)
     : isolate_(isolate),
       nesting_(0),
       extensions_cache_(Script::TYPE_EXTENSION) {}
 
 template <class Source>
@@ skipping 2814 matching lines @@
     // exposing debug global object doesn't make much sense).
     debug_context->set_security_token(native_context->security_token());
     Handle<String> debug_string =
         factory->InternalizeUtf8String(FLAG_expose_debug_as);
     uint32_t index;
     if (debug_string->AsArrayIndex(&index)) return true;
     Handle<Object> global_proxy(debug_context->global_proxy(), isolate);
     JSObject::AddProperty(global, debug_string, global_proxy, DONT_ENUM);
   }
 
+#if defined(V8_WASM)
   if (FLAG_expose_wasm) {
     WasmJs::Install(isolate, global);
   }
+#endif
 
   return true;
 }
 
 
 static uint32_t Hash(RegisteredExtension* extension) {
   return v8::internal::ComputePointerHash(extension);
 }
 
 
@@ skipping 479 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8