Fix some more shorten-64-to-32 warnings:

runtime/vm/class_table.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_CLASS_TABLE_H_
 #define VM_CLASS_TABLE_H_
 
 #include "platform/assert.h"
 #include "vm/bitfield.h"
 #include "vm/globals.h"
@@ skipping 114 matching lines @@
 
   void set_trace_allocation(bool trace_allocation) {
     state_ = TraceAllocationBit::update(trace_allocation, state_);
   }
 
  private:
   enum StateBits {
     kTraceAllocationBit = 0,
   };
 
-  class TraceAllocationBit : public BitField<bool, kTraceAllocationBit, 1> {};
+  class TraceAllocationBit :
+      public BitField<intptr_t, bool, kTraceAllocationBit, 1> {};
 
   // Recent old at start of last new GC (used to compute promoted_*).
   intptr_t old_pre_new_gc_count_;
   intptr_t old_pre_new_gc_size_;
   intptr_t state_;
 };
 
 
 class ClassTable {
  public:
@@ skipping 99 matching lines @@
   ClassHeapStats* PreliminaryStatsAt(intptr_t cid);
   void UpdateLiveOld(intptr_t cid, intptr_t size, intptr_t count = 1);
   void UpdateLiveNew(intptr_t cid, intptr_t size);
 
   DISALLOW_COPY_AND_ASSIGN(ClassTable);
 };
 
 }  // namespace dart
 
 #endif  // VM_CLASS_TABLE_H_