[asmjs] Use char predicates to scan asm.js rather than manually compare

Change-Id: I142735622cb741fa8d84ec1036febb720a467363
Reviewed-on: https://chromium-review.googlesource.com/1109918Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53928}

src/asmjs/asm-scanner.cc

@@ -4,6 +4,7 @@
 
 #include "src/asmjs/asm-scanner.h"
 
+#include "src/char-predicates-inl.h"
 #include "src/conversions.h"
 #include "src/flags.h"
 #include "src/parsing/scanner.h"
@@ -413,16 +414,13 @@ void AsmJsScanner::ConsumeCompareOrShift(uc32 ch) {
 }
 
 bool AsmJsScanner::IsIdentifierStart(uc32 ch) {
-  return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || ch == '_' ||
-         ch == '$';
+  return IsInRange(AsciiAlphaToLower(ch), 'a', 'z') || ch == '_' || ch == '$';
 }
 
-bool AsmJsScanner::IsIdentifierPart(uc32 ch) {
-  return IsIdentifierStart(ch) || (ch >= '0' && ch <= '9');
-}
+bool AsmJsScanner::IsIdentifierPart(uc32 ch) { return IsAsciiIdentifier(ch); }
 
 bool AsmJsScanner::IsNumberStart(uc32 ch) {
-  return ch == '.' || (ch >= '0' && ch <= '9');
+  return ch == '.' || IsDecimalDigit(ch);
 }
 
 }  // namespace internal