Introduce per-isolate assert scopes and API to guard JS execution.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6496 matching lines @@
   isolate->Enter();
 }
 
 
 void Isolate::Exit() {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   isolate->Exit();
 }
 
 
+Isolate::DisallowJavascriptExecutionScope::DisallowJavascriptExecutionScope(
+    Isolate* isolate) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  internal_ = reinterpret_cast<void*>(
+      new i::DisallowJavascriptExecution(i_isolate));
+}
+
+
+Isolate::DisallowJavascriptExecutionScope::~DisallowJavascriptExecutionScope() {
+  delete reinterpret_cast<i::DisallowJavascriptExecution*>(internal_);
+}
+
+
+Isolate::AllowJavascriptExecutionScope::AllowJavascriptExecutionScope(
+    Isolate* isolate) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  internal_ = reinterpret_cast<void*>(
+      new i::AllowJavascriptExecution(i_isolate));
+}
+
+
+Isolate::AllowJavascriptExecutionScope::~AllowJavascriptExecutionScope() {
+  delete reinterpret_cast<i::AllowJavascriptExecution*>(internal_);
+}
+
+
 void Isolate::GetHeapStatistics(HeapStatistics* heap_statistics) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   if (!isolate->IsInitialized()) {
     heap_statistics->total_heap_size_ = 0;
     heap_statistics->total_heap_size_executable_ = 0;
     heap_statistics->total_physical_size_ = 0;
     heap_statistics->used_heap_size_ = 0;
     heap_statistics->heap_size_limit_ = 0;
     return;
   }
@@ skipping 978 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal