[builtins] Create StringToNumber helper.

src/code-stub-assembler.h

Index: src/code-stub-assembler.h
diff --git a/src/code-stub-assembler.h b/src/code-stub-assembler.h
index 30000c390ce5b9da95ca527ca66ac9b50627e68a..1ea15737f5c3e2fd42e7ce40e74c4ffb23365b20 100644
--- a/src/code-stub-assembler.h
+++ b/src/code-stub-assembler.h
@@ -354,6 +354,11 @@ class CodeStubAssembler : public compiler::CodeAssembler {
   // Return the single character string with only {code}.
   compiler::Node* StringFromCharCode(compiler::Node* code);
 
+  // Type conversion helpers.
+  // Convert a String to a Number.
+  compiler::Node* StringToNumber(compiler::Node* context,
+                                 compiler::Node* input);
+
   // Returns a node that is true if the given bit is set in |word32|.
   template <typename T>
   compiler::Node* BitFieldDecode(compiler::Node* word32) {