Move some Runtime:: functions and remove runtime.h as include when unnecessary.

src/runtime/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_
+#ifndef V8_RUNTIME_STRING_BUILDER_H_
+#define V8_RUNTIME_STRING_BUILDER_H_
 
 namespace v8 {
 namespace internal {
 
 const int kStringBuilderConcatHelperLengthBits = 11;
 const int kStringBuilderConcatHelperPositionBits = 19;
 
 typedef BitField<int, 0, kStringBuilderConcatHelperLengthBits>
     StringBuilderSubstringLength;
 typedef BitField<int, kStringBuilderConcatHelperLengthBits,
@@ skipping 269 matching lines @@
 
   Heap* heap_;
   FixedArrayBuilder array_builder_;
   Handle<String> subject_;
   int character_count_;
   bool is_one_byte_;
 };
 }
 }  // namespace v8::internal
 
-#endif  // V8_STRING_BUILDER_H_
+#endif  // V8_RUNTIME_STRING_BUILDER_H_