Sharing of descriptor arrays.

src/arm/macro-assembler-arm.h

Index: src/arm/macro-assembler-arm.h
diff --git a/src/arm/macro-assembler-arm.h b/src/arm/macro-assembler-arm.h
index 8eb97125eab14ddb0f7a12fa1a97d8341b2679bd..7d127b5e8781f6086ceaacc0c5c50ece65b8adf3 100644
--- a/src/arm/macro-assembler-arm.h
+++ b/src/arm/macro-assembler-arm.h
@@ -1273,6 +1273,15 @@ class MacroAssembler: public Assembler {
                                Register descriptors,
                                Register scratch);
   void EnumLength(Register dst, Register map);
+  void NumberOfOwnDescriptors(Register dst, Register map);
+
+  template<typename Field>
+  void DecodeField(Register reg) {
+    static const int shift = Field::kShift;
+    static const int mask = (Field::kMask >> shift) << kSmiTagSize;
+    mov(reg, Operand(reg, LSR, shift));
+    and_(reg, reg, Operand(mask));
+  }
 
   // Activation support.
   void EnterFrame(StackFrame::Type type);