Add AccessibleObject and Field to mirror

Main motivation is to remove all the functionality / field access on
java side to ArtField. Also comes with some reflection speedups /
slowdowns.

Summary results:
getDeclaredField/getField are slower mostly due to JNI overhead.
However, there is a large speedup in getInt, setInt,
GetInstanceField, and GetStaticField.

Before timings (N5 --compiler-filter=everything):

                       benchmark      ns linear runtime
          Class_getDeclaredField  782.86 ===
                  Class_getField  832.77 ===
                    Field_getInt  160.17 =
                    Field_setInt  195.88 =
                GetInstanceField 3214.38 ==============
                  GetStaticField 6809.49 ==============================

After:
          Class_getDeclaredField 1068.15 ============
                  Class_getField 1180.00 ==============
                    Field_getInt  121.85 =
                    Field_setInt  139.98 =
                GetInstanceField 1986.15 =======================
                  GetStaticField 2523.63 ==============================

Bug: 19264997

Change-Id: Ic0d0fc1b56b95cd6d60f8e76f19caeaa23045c77
diff --git a/runtime/mirror/accessible_object.h b/runtime/mirror/accessible_object.h
new file mode 100644
index 0000000..6d4c0f6
--- /dev/null
+++ b/runtime/mirror/accessible_object.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_MIRROR_ACCESSIBLE_OBJECT_H_
+#define ART_RUNTIME_MIRROR_ACCESSIBLE_OBJECT_H_
+
+#include "class.h"
+#include "gc_root.h"
+#include "object.h"
+#include "object_callbacks.h"
+#include "read_barrier_option.h"
+#include "thread.h"
+
+namespace art {
+
+namespace mirror {
+
+// C++ mirror of java.lang.reflect.AccessibleObject
+class MANAGED AccessibleObject : public Object {
+ public:
+  static MemberOffset FlagOffset() {
+    return OFFSET_OF_OBJECT_MEMBER(AccessibleObject, flag_);
+  }
+
+  template<bool kTransactionActive>
+  void SetAccessible(bool value) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    UNUSED(padding_);
+    return SetFieldBoolean<kTransactionActive>(FlagOffset(), value ? 1u : 0u);
+  }
+
+  bool IsAccessible() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    return GetFieldBoolean(FlagOffset());
+  }
+
+ private:
+  uint8_t flag_;
+  // Padding required for now since "packed" will cause reflect.Field fields to not be aligned
+  // otherwise.
+  uint8_t padding_[3];
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(AccessibleObject);
+};
+
+}  // namespace mirror
+}  // namespace art
+
+#endif  // ART_RUNTIME_MIRROR_ACCESSIBLE_OBJECT_H_