expose AssertNoAllocation to api

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 4352ef3301e2f56a44689bc27459219b8cf1961e..4546e85b7855c64007ac934917cf2698df5474ef 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -6039,6 +6039,20 @@ Local<Integer> v8::Integer::NewFromUnsigned(uint32_t value, Isolate* isolate) {
 }
 
 
+#ifdef DEBUG
+v8::AssertNoGCScope::AssertNoGCScope(v8::Isolate* isolate)
+  : isolate_(isolate),
+    data_(i::EnterAllocationScope(
+        reinterpret_cast<i::Isolate*>(isolate), false)) {
+  STATIC_ASSERT(sizeof(data_) == sizeof(i::AllocationScopeData));
+}
+
+v8::AssertNoGCScope::~AssertNoGCScope() {
+  i::ExitAllocationScope(reinterpret_cast<i::Isolate*>(isolate_), data_);
+}
+#endif
+
+
 void V8::IgnoreOutOfMemoryException() {
   EnterIsolateIfNeeded()->set_ignore_out_of_memory(true);
 }