Introduce a VM type cast to avoid repeating a type test and spare a handle.

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 74 matching lines @@
         VMHandles::AllocateZoneHandle(isolate));                               \
     initializeHandle(obj, raw_ptr);                                            \
     if (!obj->Is##object()) {                                                  \
       FATAL("Handle check failed.");                                           \
     }                                                                          \
     return *obj;                                                               \
   }                                                                            \
   static object& CheckedZoneHandle(RawObject* raw_ptr) {                       \
     return CheckedZoneHandle(Isolate::Current(), raw_ptr);                     \
   }                                                                            \
+  static const object& Cast(const Object& obj) {                               \
+    ASSERT(obj.Is##object());                                                  \
+    return reinterpret_cast<const object&>(obj);                               \
+  }                                                                            \
   static Raw##object* null() {                                                 \
     return reinterpret_cast<Raw##object*>(Object::null());                     \
   }                                                                            \
   virtual const char* ToCString() const;                                       \
   static const ObjectKind kInstanceKind = k##object;                           \
  protected:  /* NOLINT */                                                      \
   object() : super() {}                                                        \
  private:  /* NOLINT */                                                        \
   /* Initialize the handle based on the raw_ptr in the presence of null. */    \
   static void initializeHandle(object* obj, RawObject* raw_ptr) {              \
@@ skipping 4982 matching lines @@
 }
 
 
 intptr_t Stackmap::SizeInBits() const {
   return (Smi::Value(raw_ptr()->bitmap_size_in_bytes_) * kBitsPerByte);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_