Support unaligned integer loads on ARM and MIPS.

runtime/vm/assembler_arm64.h

Index: runtime/vm/assembler_arm64.h
diff --git a/runtime/vm/assembler_arm64.h b/runtime/vm/assembler_arm64.h
index 1f8edfa2e89ea563abf417ceaeab2292ecdef7b9..4210ed525cd99ff744468af5ebf4a622b572f6b1 100644
--- a/runtime/vm/assembler_arm64.h
+++ b/runtime/vm/assembler_arm64.h
@@ -1401,12 +1401,30 @@ class Assembler : public ValueObject {
                                     intptr_t index_scale,
                                     Register array,
                                     intptr_t index) const;
+  void LoadElementAddressForIntIndex(Register address,
+                                     bool is_external,
+                                     intptr_t cid,
+                                     intptr_t index_scale,
+                                     Register array,
+                                     intptr_t index);
   Address ElementAddressForRegIndex(bool is_load,
                                     bool is_external,
                                     intptr_t cid,
                                     intptr_t index_scale,
                                     Register array,
                                     Register index);
+  void LoadElementAddressForRegIndex(Register address,
+                                     bool is_load,
+                                     bool is_external,
+                                     intptr_t cid,
+                                     intptr_t index_scale,
+                                     Register array,
+                                     Register index);
+
+  void LoadUnaligned(Register dst, Register addr, Register tmp,
+                     OperandSize sz);
+  void StoreUnaligned(Register src, Register addr, Register tmp,
+                      OperandSize sz);
 
  private:
   AssemblerBuffer buffer_;  // Contains position independent code.