Introduce JavascriptExecutionObserver scope.

src/execution.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/execution.h"
 
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/isolate-inl.h"
@@ skipping 50 matching lines @@
   DCHECK(!receiver->IsJSGlobalObject());
 
   // Entering JavaScript.
   VMState<JS> state(isolate);
   CHECK(AllowJavascriptExecution::IsAllowed(isolate));
   if (!ThrowOnJavascriptExecution::IsAllowed(isolate)) {
     isolate->ThrowIllegalOperation();
     isolate->ReportPendingMessages();
     return MaybeHandle<Object>();
   }
+  JavascriptExecutionObserver::SetObserved(isolate);
 
   // Placeholder for return value.
   Object* value = NULL;
 
   typedef Object* (*JSEntryFunction)(Object* new_target, Object* target,
                                      Object* receiver, int argc,
                                      Object*** args);
 
   Handle<Code> code = is_construct
       ? isolate->factory()->js_construct_entry_code()
@@ skipping 447 matching lines @@
     isolate_->InvokeApiInterruptCallbacks();
   }
 
   isolate_->counters()->stack_interrupts()->Increment();
   isolate_->counters()->runtime_profiler_ticks()->Increment();
   isolate_->runtime_profiler()->OptimizeNow();
 
   return isolate_->heap()->undefined_value();
 }
 
+
+JavascriptExecutionObserver::JavascriptExecutionObserver(Isolate* isolate)
+    : isolate_(isolate), observed_(false) {
+  prev_ = isolate->execution_observer();
+  isolate->set_execution_observer(this);
+}
+
+
+JavascriptExecutionObserver::~JavascriptExecutionObserver() {
+  isolate_->set_execution_observer(prev_);
+}
+
+
+void JavascriptExecutionObserver::SetObserved(Isolate* isolate) {
+  for (JavascriptExecutionObserver* observer = isolate->execution_observer();
+       observer != NULL; observer = observer->prev_) {
+    // If this observer is already set to true, so are all its predecessors.
+    if (observer->observed_) break;
+    observer->observed_ = true;
+  }
+}
+
 }  // namespace internal
 }  // namespace v8