Avoid triggering an ASSERT in TypedData

runtime/vm/kernel_to_il.h

 // Copyright (c) 2016, 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.
 
 #ifndef RUNTIME_VM_KERNEL_TO_IL_H_
 #define RUNTIME_VM_KERNEL_TO_IL_H_
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
 
 #include "vm/growable_array.h"
@@ skipping 266 matching lines @@
   void SetStringOffsets(const TypedData& string_offsets);
 
   const TypedData& string_data() { return string_data_; }
   void SetStringData(const TypedData& string_data);
 
   const TypedData& canonical_names() { return canonical_names_; }
   void SetCanonicalNames(const TypedData& canonical_names);
 
   intptr_t StringOffset(StringIndex index) const;
   intptr_t StringSize(StringIndex index) const;
+
+  // The address of the backing store of the string with a given index.  If the
+  // backing store is in the VM's heap this address is not safe for GC (call the
+  // function and use the result within a NoSafepointScope).
+  uint8_t* StringBuffer(StringIndex index) const;
+
   uint8_t CharacterAt(StringIndex string_index, intptr_t index);
   bool StringEquals(StringIndex string_index, const char* other);
 
   // Accessors and predicates for canonical names.
   NameIndex CanonicalNameParent(NameIndex name);
   StringIndex CanonicalNameString(NameIndex name);
   bool IsAdministrative(NameIndex name);
   bool IsPrivate(NameIndex name);
   bool IsRoot(NameIndex name);
   bool IsLibrary(NameIndex name);
@@ skipping 639 matching lines @@
 namespace kernel {
 
 RawObject* EvaluateMetadata(const Field& metadata_field);
 RawObject* BuildParameterDescriptor(const Function& function);
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 #endif  // RUNTIME_VM_KERNEL_TO_IL_H_