[Interpreter] Always store current context in the frames context slot.

test/mjsunit/deopt-with-outer-context.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+function outer(y) {
+  function inner() {
+    var x = 10;
+    (function() {
+       // Access x from inner function to force it to be context allocated.
+       x = 20;
+       %DeoptimizeFunction(inner);
+    })();
+    // Variable y should be read from the outer context.
+    return y;
+  };
+  %OptimizeFunctionOnNextCall(inner);
+  return inner();
+}
+
+assertEquals(30, outer(30));