Introduce LanguageMode, drop StrictMode.

src/runtime/runtime-debug.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/v8.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/debug.h"
 #include "src/deoptimizer.h"
@@ skipping 614 matching lines @@
 
   // Add the value being returned.
   if (at_return) {
     details->set(details_index++, *return_value);
   }
 
   // Add the receiver (same as in function frame).
   // THIS MUST BE DONE LAST SINCE WE MIGHT ADVANCE
   // THE FRAME ITERATOR TO WRAP THE RECEIVER.
   Handle<Object> receiver(it.frame()->receiver(), isolate);
-  if (!receiver->IsJSObject() && shared->strict_mode() == SLOPPY &&
+  if (!receiver->IsJSObject() && is_sloppy(shared->language_mode()) &&
       !function->IsBuiltin()) {
     // If the receiver is not a JSObject and the function is not a
     // builtin or strict-mode we have hit an optimization where a
     // value object is not converted into a wrapped JS objects. To
     // hide this optimization from the debugger, we wrap the receiver
     // by creating correct wrapper object based on the calling frame's
     // native context.
     it.Advance();
     if (receiver->IsUndefined()) {
       receiver = handle(function->global_proxy());
@@ skipping 2163 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(RuntimeReference_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }
 }  // namespace v8::internal