AllocationProfiler: introduce allocation_profiler flag in V8 api.

test/cctest/test-heap-profiler.cc

Index: test/cctest/test-heap-profiler.cc
diff --git a/test/cctest/test-heap-profiler.cc b/test/cctest/test-heap-profiler.cc
index db2243a3f0445f847838d5bbe984ef6df5ffe7e9..988e56de72ca0ece0643fe745245436cda9b7f8b 100644
--- a/test/cctest/test-heap-profiler.cc
+++ b/test/cctest/test-heap-profiler.cc
@@ -2062,6 +2062,18 @@ v8::DeclareExtension kHeapProfilerExtensionDeclaration(
 
 
 // This is an example of using checking of JS allocations tracking in a test.
+TEST(AllocationProfilerString) {
+  v8::internal::Isolate::Current()->enable_allocation_profiler();
+  const char* extensions[] = { HeapProfilerExtension::kName };
+  v8::ExtensionConfiguration config(1, extensions);
+  LocalContext env(&config);
+  v8::HandleScope scope(env->GetIsolate());
+  HeapObjectsTracker tracker;
+  CompileRun("var a = new String("   ");findUntrackedObjects();");
+}
+
+
+// This is an example of using checking of JS allocations tracking in a test.
 TEST(HeapObjectsTracker) {
   const char* extensions[] = { HeapProfilerExtension::kName };
   v8::ExtensionConfiguration config(1, extensions);