Ensure integrity of ASCII strings.

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index e12895a28348e011bf0bdf9cddc6c4e06f94d7cb..6c0baedd0b74bee1cd0b186a0f3f2f7189a38ebc 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -595,12 +595,24 @@ void ExternalStringTable::Iterate(ObjectVisitor* v) {
 void ExternalStringTable::Verify() {
 #ifdef DEBUG
   for (int i = 0; i < new_space_strings_.length(); ++i) {
-    ASSERT(heap_->InNewSpace(new_space_strings_[i]));
-    ASSERT(new_space_strings_[i] != HEAP->raw_unchecked_the_hole_value());
+    Object* obj = Object::cast(new_space_strings_[i]);
+    // TODO(yangguo): check that the object is indeed an external string.
+    ASSERT(heap_->InNewSpace(obj));
+    ASSERT(obj != HEAP->raw_unchecked_the_hole_value());
+    if (obj->IsExternalAsciiString()) {
+      ExternalAsciiString* string = ExternalAsciiString::cast(obj);
+      ASSERT(String::IsAscii(string->GetChars(), string->length()));
+    }
   }
   for (int i = 0; i < old_space_strings_.length(); ++i) {
-    ASSERT(!heap_->InNewSpace(old_space_strings_[i]));
-    ASSERT(old_space_strings_[i] != HEAP->raw_unchecked_the_hole_value());
+    Object* obj = Object::cast(new_space_strings_[i]);
+    // TODO(yangguo): check that the object is indeed an external string.
+    ASSERT(!heap_->InNewSpace(obj));
+    ASSERT(obj != HEAP->raw_unchecked_the_hole_value());
+    if (obj->IsExternalAsciiString()) {
+      ExternalAsciiString* string = ExternalAsciiString::cast(obj);
+      ASSERT(String::IsAscii(string->GetChars(), string->length()));
+    }
   }
 #endif
 }