Add Function based profile tree

runtime/vm/instructions_arm.h

 // Copyright (c) 2013, 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.
 // Classes that describe assembly patterns as used by inline caches.
 
 #ifndef VM_INSTRUCTIONS_ARM_H_
 #define VM_INSTRUCTIONS_ARM_H_
 
 #ifndef VM_INSTRUCTIONS_H_
 #error Do not include instructions_arm.h directly; use instructions.h instead.
@@ skipping 78 matching lines @@
   bool IsValid() const;
   uword TargetAddress() const;
   void SetTargetAddress(uword target_address) const;
 
  private:
   const uword pc_;
 
   DISALLOW_COPY_AND_ASSIGN(JumpPattern);
 };
 
+
+class ReturnPattern : public ValueObject {
+ public:
+  explicit ReturnPattern(uword pc);
+
+  // bx_lr = 1.
+  static const int kLengthInBytes = 1 * Instr::kInstrSize;
+
+  int pattern_length_in_bytes() const {
+    return kLengthInBytes;
+  }
+
+  bool IsValid() const;
+
+ private:
+  const uword pc_;
+};
+
 }  // namespace dart
 
 #endif  // VM_INSTRUCTIONS_ARM_H_