Fix bug in Utf8::CodePointCount which was causing some strings with latin1

vm/dart_api_impl_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
 #include "platform/utils.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
@@ skipping 495 matching lines @@
     EXPECT_VALID(result);
     int64_t value;
     result = Dart_IntegerToInt64(result, &value);
     EXPECT_VALID(result);
     EXPECT_EQ(i, value);
   }
 }
 
 
 TEST_CASE(IsString) {
+  uint8_t latin1[] = { 'o', 'n', 'e', 0xC2, 0xA2 };
+
+  Dart_Handle latin1str = Dart_NewStringFromUTF8(latin1, ARRAY_SIZE(latin1));
+  EXPECT_VALID(latin1str);
+  EXPECT(Dart_IsString(latin1str));
+  EXPECT(Dart_IsStringLatin1(latin1str));
+  EXPECT(!Dart_IsExternalString(latin1str));
+  intptr_t len = -1;
+  EXPECT_VALID(Dart_StringLength(latin1str, &len));
+  EXPECT_EQ(4, len);
+
   uint8_t data8[] = { 'o', 'n', 'e', 0x7F };
 
   Dart_Handle str8 = Dart_NewStringFromUTF8(data8, ARRAY_SIZE(data8));
   EXPECT_VALID(str8);
   EXPECT(Dart_IsString(str8));
   EXPECT(Dart_IsStringLatin1(str8));
   EXPECT(!Dart_IsExternalString(str8));
 
   Dart_Handle ext8 = Dart_NewExternalLatin1String(data8, ARRAY_SIZE(data8),
                                                   NULL, NULL);
@@ skipping 6812 matching lines @@
   Dart_LoadSource(TestCase::lib(), url, source);
 
   dart_args[0] = Dart_NewInteger(1);
   result = Dart_Invoke(lib1, NewString("start"), 1, dart_args);
   EXPECT_VALID(result);
 }
 
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart