Implement new Function.prototype.toString and fix CreateDynamicFunction parsing

src/string-builder.h

 // Copyright 2014 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_STRING_BUILDER_H_
 #define V8_STRING_BUILDER_H_
 
 #include "src/assert-scope.h"
 #include "src/factory.h"
 #include "src/handles.h"
@@ skipping 292 matching lines @@
   INLINE(bool CurrentPartCanFit(int length)) {
     return part_length_ - current_index_ > length;
   }
 
   void AppendString(Handle<String> string);
 
   MaybeHandle<String> Finish();
 
   INLINE(bool HasOverflowed()) const { return overflowed_; }
 
+  INLINE(int Length()) const { return accumulator_->length() + current_index_; }
+
   // Change encoding to two-byte.
   void ChangeEncoding() {
     DCHECK_EQ(String::ONE_BYTE_ENCODING, encoding_);
     ShrinkCurrentPart();
     encoding_ = String::TWO_BYTE_ENCODING;
     Extend();
   }
 
   template <typename DestChar>
   class NoExtend {
@@ skipping 114 matching lines @@
     DCHECK_EQ(String::TWO_BYTE_ENCODING, encoding_);
     SeqTwoByteString::cast(*current_part_)
         ->SeqTwoByteStringSet(current_index_++, c);
   }
   if (current_index_ == part_length_) Extend();
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_STRING_BUILDER_H_