Fix issue 17514770 (https://b2.corp.google.com/issues/17514770)

runtime/vm/object.h

 // 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.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 2870 matching lines @@
     return raw_ptr()->is_dart_scheme_;
   }
   void set_is_dart_scheme(bool value) const {
     raw_ptr()->is_dart_scheme_ = value;
   }
 
   bool IsCoreLibrary() const {
     return raw() == CoreLibrary();
   }
 
+  inline intptr_t UrlHash() const;
+
   static RawLibrary* LookupLibrary(const String& url);
   static RawLibrary* GetLibrary(intptr_t index);
 
   static void InitCoreLibrary(Isolate* isolate);
   static void InitNativeWrappersLibrary(Isolate* isolate);
 
   static RawLibrary* AsyncLibrary();
   static RawLibrary* ConvertLibrary();
   static RawLibrary* CoreLibrary();
   static RawLibrary* CollectionLibrary();
@@ skipping 4544 matching lines @@
   }
   for (intptr_t i = 0; i < len; i++) {
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 
+intptr_t Library::UrlHash() const {
+  intptr_t result = Smi::Value(url()->ptr()->hash_);
+  ASSERT(result != 0);
+  return result;
+}
+
+
 void MegamorphicCache::SetEntry(const Array& array,
                                 intptr_t index,
                                 const Smi& class_id,
                                 const Function& target) {
   array.SetAt((index * kEntryLength) + kClassIdIndex, class_id);
   array.SetAt((index * kEntryLength) + kTargetFunctionIndex, target);
 }
 
 
 RawObject* MegamorphicCache::GetClassId(const Array& array, intptr_t index) {
   return array.At((index * kEntryLength) + kClassIdIndex);
 }
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_