Move platform abstraction to base library

src/json-parser.h

 // Copyright 2011 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_JSON_PARSER_H_
 #define V8_JSON_PARSER_H_
 
 #include "src/v8.h"
 
 #include "src/char-predicates-inl.h"
@@ skipping 510 matching lines @@
       Advance();
     } while (c0_ >= '0' && c0_ <= '9');
   }
   int length = position_ - beg_pos;
   double number;
   if (seq_ascii) {
     Vector<const uint8_t> chars(seq_source_->GetChars() +  beg_pos, length);
     number = StringToDouble(isolate()->unicode_cache(),
                             chars,
                             NO_FLAGS,  // Hex, octal or trailing junk.
-                            OS::nan_value());
+                            base::OS::nan_value());
   } else {
     Vector<uint8_t> buffer = Vector<uint8_t>::New(length);
     String::WriteToFlat(*source_, buffer.start(), beg_pos, position_);
     Vector<const uint8_t> result =
         Vector<const uint8_t>(buffer.start(), length);
     number = StringToDouble(isolate()->unicode_cache(),
                             result,
                             NO_FLAGS,  // Hex, octal or trailing junk.
                             0.0);
     buffer.Dispose();
@@ skipping 241 matching lines @@
 
   ASSERT_EQ('"', c0_);
   // Advance past the last '"'.
   AdvanceSkipWhitespace();
   return result;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_PARSER_H_