Load callback data from weak cell instead of embedding it in handler.

src/arm64/macro-assembler-arm64.h

Index: src/arm64/macro-assembler-arm64.h
diff --git a/src/arm64/macro-assembler-arm64.h b/src/arm64/macro-assembler-arm64.h
index fbb7d5b4fbac161c650471fe3d61cb4cb4fe7329..3a0df0b04926bce5e68bffba7ddb9b0ff40902ff 100644
--- a/src/arm64/macro-assembler-arm64.h
+++ b/src/arm64/macro-assembler-arm64.h
@@ -1472,6 +1472,8 @@ class MacroAssembler : public Assembler {
   // Compare the given value and the value of weak cell.
   void CmpWeakValue(Register value, Handle<WeakCell> cell, Register scratch);
 
+  void GetWeakValue(Register value, Handle<WeakCell> cell);
+
   // Load the value of the weak cell in the value register. Branch to the given
   // miss label if the weak cell was cleared.
   void LoadWeakValue(Register value, Handle<WeakCell> cell, Label* miss);