[builtins] Create StringToNumber helper.

src/code-stub-assembler.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CODE_STUB_ASSEMBLER_H_
 #define V8_CODE_STUB_ASSEMBLER_H_
 
 #include <functional>
 
 #include "src/compiler/code-assembler.h"
@@ skipping 336 matching lines @@
                               PrimitiveType primitive_type,
                               char const* method_name);
 
   // String helpers.
   // Load a character from a String (might flatten a ConsString).
   compiler::Node* StringCharCodeAt(compiler::Node* string,
                                    compiler::Node* smi_index);
   // 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) {
     return BitFieldDecode(word32, T::kShift, T::kMask);
   }
 
   compiler::Node* BitFieldDecode(compiler::Node* word32, uint32_t shift,
                                  uint32_t mask);
 
   void SetCounter(StatsCounter* counter, int value);
@@ skipping 241 matching lines @@
   compiler::Node* SmiShiftBitsConstant();
 
   static const int kElementLoopUnrollThreshold = 8;
 };
 
 DEFINE_OPERATORS_FOR_FLAGS(CodeStubAssembler::AllocationFlags);
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_CODE_STUB_ASSEMBLER_H_