Optimize LocalVarDescriptor objects for functions that have no local variables

runtime/vm/raw_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_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/atomic.h"
 #include "vm/globals.h"
@@ skipping 1084 matching lines @@
     }
   };
 
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(LocalVarDescriptors);
   RawArray* names_;  // Array of [length_] variable names.
   int32_t length_;  // Number of descriptors.
 
   // Variable info with [length_] entries.
   VarInfo* data() { OPEN_ARRAY_START(VarInfo, int32_t); }
+
+  friend class Object;
 };
 
 
 class RawExceptionHandlers : public RawObject {
  public:
   // The index into the ExceptionHandlers table corresponds to
   // the try_index of the handler.
   struct HandlerInfo {
     intptr_t handler_pc;       // PC value of handler.
     int16_t outer_try_index;   // Try block index of enclosing try block.
@@ skipping 919 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_