Tweak the TurboFan pipeline for stub compilation.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index 7d82dfa8463fac3305ca98f42dd9a5545444a40c..679627788d066f16662f0287b51f09ae7fd77ff8 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -694,3 +694,14 @@ function ToPositiveInteger(x, rangeErrorName) {
 // that is cloned when running the code.  It is essential that the
 // boilerplate gets the right prototype.
 %FunctionSetPrototype($Array, new $Array(0));
+
+
+/* -----------------------------------------------
+   - - -   J a v a S c r i p t   S t u b s   - - -
+   -----------------------------------------------
+*/
+
+function STRING_LENGTH_STUB(name) {
+  var receiver = this;  // implicit first parameter
+  return %_StringLength(%_JSValueValue(receiver));
+}