Support FrameLookup vm test on ARM, requiring among other things:

runtime/vm/assembler_arm.h

Index: runtime/vm/assembler_arm.h
===================================================================
--- runtime/vm/assembler_arm.h	(revision 20887)
+++ runtime/vm/assembler_arm.h	(working copy)
@@ -251,8 +251,8 @@
     encoding_ |= static_cast<uint32_t>(rn) << kRnShift;
   }
 
-  explicit Address(Register rn, Register rm, Shift shift = LSL,
-                   uint32_t shift_imm = 0, Mode am = Offset) {
+  Address(Register rn, Register rm,
+          Shift shift = LSL, uint32_t shift_imm = 0, Mode am = Offset) {
     ShifterOperand so(rm, shift, shift_imm);
 
     kind_ = ShiftedRegister;
@@ -639,8 +639,8 @@
 
   // Set up a stub frame so that the stack traversal code can easily identify
   // a stub frame.
-  void EnterStubFrame();
-  void LeaveStubFrame();
+  void EnterStubFrame(bool uses_pp = false);
+  void LeaveStubFrame(bool uses_pp = false);
 
   // Instruction pattern from entrypoint is used in Dart frame prologs
   // to set up the frame and save a PC which can be used to figure out the