Simplify invokeCallback() and support void return values for IDL callbacks

Source/bindings/v8/custom/V8SQLTransactionCustom.cpp

Index: Source/bindings/v8/custom/V8SQLTransactionCustom.cpp
diff --git a/Source/bindings/v8/custom/V8SQLTransactionCustom.cpp b/Source/bindings/v8/custom/V8SQLTransactionCustom.cpp
index be2c45f7fb784e977a5c8740f33265f7aa194913..9a314b5f6669fedcce9c2435a8dbd223f297410f 100644
--- a/Source/bindings/v8/custom/V8SQLTransactionCustom.cpp
+++ b/Source/bindings/v8/custom/V8SQLTransactionCustom.cpp
@@ -96,7 +96,7 @@ void V8SQLTransaction::executeSqlMethodCustom(const v8::FunctionCallbackInfo<v8:
             setDOMException(TypeMismatchError, info.GetIsolate());
             return;
         }
-        callback = V8SQLStatementCallback::create(v8::Handle<v8::Object>::Cast(info[2]), executionContext);
+        callback = V8SQLStatementCallback::create(v8::Handle<v8::Function>::Cast(info[2]), executionContext);
     }
 
     OwnPtr<SQLStatementErrorCallback> errorCallback;
@@ -105,7 +105,7 @@ void V8SQLTransaction::executeSqlMethodCustom(const v8::FunctionCallbackInfo<v8:
             setDOMException(TypeMismatchError, info.GetIsolate());
             return;
         }
-        errorCallback = V8SQLStatementErrorCallback::create(v8::Handle<v8::Object>::Cast(info[3]), executionContext);
+        errorCallback = V8SQLStatementErrorCallback::create(v8::Handle<v8::Function>::Cast(info[3]), executionContext);
     }
 
     ExceptionState exceptionState(info.Holder(), info.GetIsolate());