Call directly to c callbacks in Invoke instead of transitioning to js and back out.

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 40 matching lines @@
 
 
 MUST_USE_RESULT static MaybeHandle<Object> Invoke(
     bool is_construct,
     Handle<JSFunction> function,
     Handle<Object> receiver,
     int argc,
     Handle<Object> args[]) {
   Isolate* isolate = function->GetIsolate();
 
+  // api callbacks can be called directly.
+  if (!is_construct && function->shared()->IsApiFunction()) {
+    SaveContext save(isolate);
+    isolate->set_context(function->context());
+    if (receiver->IsGlobalObject()) {
+      receiver = handle(Handle<GlobalObject>::cast(receiver)->global_proxy());
+    }
+    DCHECK(function->context()->global_object()->IsGlobalObject());
+    auto value = Builtins::InvokeApiFunction(function, receiver, argc, args);
+    bool has_exception = value.is_null();
+    DCHECK(has_exception == isolate->has_pending_exception());
+    if (has_exception) {
+      isolate->ReportPendingMessages();
+      return MaybeHandle<Object>();
+    } else {
+      isolate->clear_pending_message();
+    }
+    return value;
+  }
+
   // Entering JavaScript.
   VMState<JS> state(isolate);
   CHECK(AllowJavascriptExecution::IsAllowed(isolate));
   if (!ThrowOnJavascriptExecution::IsAllowed(isolate)) {
     isolate->ThrowIllegalOperation();
     isolate->ReportPendingMessages();
     return MaybeHandle<Object>();
   }
 
   // Placeholder for return value.
@@ skipping 654 matching lines @@
   }
 
   isolate_->counters()->stack_interrupts()->Increment();
   isolate_->counters()->runtime_profiler_ticks()->Increment();
   isolate_->runtime_profiler()->OptimizeNow();
 
   return isolate_->heap()->undefined_value();
 }
 
 } }  // namespace v8::internal