Fix -Wsign-compare warnings in parser, scanner, regexp, runtime.

src/parsing/scanner.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.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #ifndef V8_PARSING_SCANNER_H_
 #define V8_PARSING_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 351 matching lines @@
       DCHECK(is_one_byte_);
       DCHECK(IsValidAscii(code_unit));
       backing_store_[position_] = static_cast<byte>(code_unit);
       position_ += kOneByteSize;
       return;
     }
 
     INLINE(void AddChar(uc32 code_unit)) {
       if (position_ >= backing_store_.length()) ExpandBuffer();
       if (is_one_byte_) {
-        if (code_unit <= unibrow::Latin1::kMaxChar) {
+        if (code_unit <= static_cast<uc32>(unibrow::Latin1::kMaxChar)) {
           backing_store_[position_] = static_cast<byte>(code_unit);
           position_ += kOneByteSize;
           return;
         }
         ConvertToTwoByte();
       }
-      if (code_unit <= unibrow::Utf16::kMaxNonSurrogateCharCode) {
+      if (code_unit <=
+          static_cast<uc32>(unibrow::Utf16::kMaxNonSurrogateCharCode)) {
         *reinterpret_cast<uint16_t*>(&backing_store_[position_]) = code_unit;
         position_ += kUC16Size;
       } else {
         *reinterpret_cast<uint16_t*>(&backing_store_[position_]) =
             unibrow::Utf16::LeadSurrogate(code_unit);
         position_ += kUC16Size;
         if (position_ >= backing_store_.length()) ExpandBuffer();
         *reinterpret_cast<uint16_t*>(&backing_store_[position_]) =
             unibrow::Utf16::TrailSurrogate(code_unit);
         position_ += kUC16Size;
@@ skipping 414 matching lines @@
   bool found_html_comment_;
 
   MessageTemplate::Template scanner_error_;
   Location scanner_error_location_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_SCANNER_H_