Fix some more shorten-64-to-32 warnings:

runtime/platform/utils.h

Index: runtime/platform/utils.h
diff --git a/runtime/platform/utils.h b/runtime/platform/utils.h
index 9e4a3846dd6b6fa3379d7629b86f540dabfa0446..508e0e7add1699321c41f28b8111e43e8236e022 100644
--- a/runtime/platform/utils.h
+++ b/runtime/platform/utils.h
@@ -204,16 +204,9 @@ class Utils {
 
   // dart2js represents integers as double precision floats, which can
   // represent anything in the range -2^53 ... 2^53.
-  static bool IsJavascriptInt64(int64_t value) {
+  static bool IsJavascriptInt(int64_t value) {
     return ((-0x20000000000000LL <= value) && (value <= 0x20000000000000LL));
   }
-  static bool IsJavascriptInt(intptr_t value) {
-#if defined(ARCH_IS_64BIT)
-    return ((-0x20000000000000LL <= value) && (value <= 0x20000000000000LL));
-#else
-    return true;
-#endif
-  }
 
   static char* StrError(int err, char* buffer, size_t bufsize);
 };