[regexp] Fix StringCharacterPosition for ThinStrings

src/regexp/regexp-macro-assembler.cc

 // Copyright 2012 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.
 
 #include "src/regexp/regexp-macro-assembler.h"
 
 #include "src/assembler.h"
 #include "src/isolate-inl.h"
 #include "src/regexp/regexp-stack.h"
 #include "src/simulator.h"
@@ skipping 115 matching lines @@
 }
 
 const byte* NativeRegExpMacroAssembler::StringCharacterPosition(
     String* subject,
     int start_index) {
   if (subject->IsConsString()) {
     subject = ConsString::cast(subject)->first();
   } else if (subject->IsSlicedString()) {
     start_index += SlicedString::cast(subject)->offset();
     subject = SlicedString::cast(subject)->parent();
-  } else if (subject->IsThinString()) {
+  }
+  if (subject->IsThinString()) {
     subject = ThinString::cast(subject)->actual();
   }
   DCHECK(start_index >= 0);
   DCHECK(start_index <= subject->length());
   if (subject->IsSeqOneByteString()) {
     return reinterpret_cast<const byte*>(
         SeqOneByteString::cast(subject)->GetChars() + start_index);
   } else if (subject->IsSeqTwoByteString()) {
     return reinterpret_cast<const byte*>(
         SeqTwoByteString::cast(subject)->GetChars() + start_index);
   } else if (subject->IsExternalOneByteString()) {
     return reinterpret_cast<const byte*>(
         ExternalOneByteString::cast(subject)->GetChars() + start_index);
   } else {
+    DCHECK(subject->IsExternalTwoByteString());
     return reinterpret_cast<const byte*>(
         ExternalTwoByteString::cast(subject)->GetChars() + start_index);
   }
 }
 
 
 int NativeRegExpMacroAssembler::CheckStackGuardState(
     Isolate* isolate, int start_index, bool is_direct_call,
     Address* return_address, Code* re_code, String** subject,
     const byte** input_start, const byte** input_end) {
@@ skipping 191 matching lines @@
   }
   *stack_base = new_stack_base;
   intptr_t stack_content_size = old_stack_base - stack_pointer;
   return new_stack_base - stack_content_size;
 }
 
 #endif  // V8_INTERPRETED_REGEXP
 
 }  // namespace internal
 }  // namespace v8