Add DartInvoke utility that returns the handle.

TEST: Building the Flutter engine.
Change-Id: If39ba005f75eb4de8650ffbda33a06ea8e841750
diff --git a/logging/dart_invoke.cc b/logging/dart_invoke.cc
index 8bc5e2b..05d86d3 100644
--- a/logging/dart_invoke.cc
+++ b/logging/dart_invoke.cc
@@ -9,15 +9,16 @@
 
 namespace tonic {
 
-bool DartInvokeField(Dart_Handle target,
-                     const char* name,
-                     std::initializer_list<Dart_Handle> args) {
+Dart_Handle DartInvokeField(Dart_Handle target,
+                            const char* name,
+                            std::initializer_list<Dart_Handle> args) {
   Dart_Handle field = Dart_NewStringFromCString(name);
-  return LogIfError(Dart_Invoke(target, field, args.size(),
-                                const_cast<Dart_Handle*>(args.begin())));
+  return Dart_Invoke(target, field, args.size(),
+                     const_cast<Dart_Handle*>(args.begin()));
 }
 
-Dart_Handle DartInvoke(Dart_Handle closure, std::initializer_list<Dart_Handle> args) {
+Dart_Handle DartInvoke(Dart_Handle closure,
+                       std::initializer_list<Dart_Handle> args) {
   int argc = args.size();
   Dart_Handle* argv = const_cast<Dart_Handle*>(args.begin());
   Dart_Handle handle = Dart_InvokeClosure(closure, argc, argv);
diff --git a/logging/dart_invoke.h b/logging/dart_invoke.h
index 49811af..4d2f115 100644
--- a/logging/dart_invoke.h
+++ b/logging/dart_invoke.h
@@ -11,11 +11,12 @@
 
 namespace tonic {
 
-bool DartInvokeField(Dart_Handle target,
-                     const char* name,
-                     std::initializer_list<Dart_Handle> args);
+Dart_Handle DartInvokeField(Dart_Handle target,
+                            const char* name,
+                            std::initializer_list<Dart_Handle> args);
 
-Dart_Handle DartInvoke(Dart_Handle closure, std::initializer_list<Dart_Handle> args);
+Dart_Handle DartInvoke(Dart_Handle closure,
+                       std::initializer_list<Dart_Handle> args);
 Dart_Handle DartInvokeVoid(Dart_Handle closure);
 
 }  // namespace tonic