IDL: make optional arguments (without default) explicit sometimes

Source/bindings/core/v8/V8ScriptRunner.cpp

Index: Source/bindings/core/v8/V8ScriptRunner.cpp
diff --git a/Source/bindings/core/v8/V8ScriptRunner.cpp b/Source/bindings/core/v8/V8ScriptRunner.cpp
index b187a3b7b995030842c064ffc17465ba0c7186df..c0d71987e0ee057c1dce578a04e6b0bd6f452046 100644
--- a/Source/bindings/core/v8/V8ScriptRunner.cpp
+++ b/Source/bindings/core/v8/V8ScriptRunner.cpp
@@ -40,6 +40,8 @@ namespace blink {
 
 namespace {
 
+const int kMaxRecursionDepth = 22;
+
 // In order to make sure all pending messages to be processed in
 // v8::Function::Call, we don't call handleMaxRecursionDepthExceeded
 // directly. Instead, we create a v8::Function of