Use the previous context link when checking context extension objects.

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index b0cc8fcf4bcd94b7c994160de23df6af5a2bad60..749d1f5dc0a3ae28a7745e6d35ebca4ffdba596e 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -1127,8 +1127,7 @@ void FullCodeGenerator::EmitLoadGlobalSlotCheckExtensions(
         __ b(ne, slow);
       }
       // Load next context in chain.
-      __ ldr(next, ContextOperand(current, Context::CLOSURE_INDEX));
-      __ ldr(next, FieldMemOperand(next, JSFunction::kContextOffset));
+      __ ldr(next, ContextOperand(current, Context::PREVIOUS_INDEX));
       // Walk the rest of the chain without clobbering cp.
       current = next;
     }
@@ -1154,8 +1153,7 @@ void FullCodeGenerator::EmitLoadGlobalSlotCheckExtensions(
     __ tst(temp, temp);
     __ b(ne, slow);
     // Load next context in chain.
-    __ ldr(next, ContextOperand(next, Context::CLOSURE_INDEX));
-    __ ldr(next, FieldMemOperand(next, JSFunction::kContextOffset));
+    __ ldr(next, ContextOperand(next, Context::PREVIOUS_INDEX));
     __ b(&loop);
     __ bind(&fast);
   }
@@ -1186,8 +1184,7 @@ MemOperand FullCodeGenerator::ContextSlotOperandCheckExtensions(
         __ tst(temp, temp);
         __ b(ne, slow);
       }
-      __ ldr(next, ContextOperand(context, Context::CLOSURE_INDEX));
-      __ ldr(next, FieldMemOperand(next, JSFunction::kContextOffset));
+      __ ldr(next, ContextOperand(context, Context::PREVIOUS_INDEX));
       // Walk the rest of the chain without clobbering cp.
       context = next;
     }