Make arm32 cpu detection recognize the DragonBoard as arm64.

runtime/vm/cpuinfo.h

 // Copyright (c) 2014, 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_CPUINFO_H_
 #define RUNTIME_VM_CPUINFO_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 
 namespace dart {
 
 // Indices into cpuinfo field name arrays.
 enum CpuInfoIndices {
   kCpuInfoProcessor = 0,
   kCpuInfoModel = 1,
   kCpuInfoHardware = 2,
   kCpuInfoFeatures = 3,
-  kCpuInfoMax = 4,
+  kCpuInfoArchitecture = 4,
+  kCpuInfoMax = 5,
 };
 
 // For Intel architectures, the method to use to get CPU information.
 enum CpuInfoMethod {
   // Use the cpuid instruction.
   kCpuInfoCpuId,
 
   // Use system calls.
   kCpuInfoSystem,
 
@@ skipping 36 matching lines @@
   // The method to use to acquire info about the CPU.
   static CpuInfoMethod method_;
 
   // Cpuinfo field names.
   static const char* fields_[kCpuInfoMax];
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_CPUINFO_H_