Test for watched expression

To begin test, open DevTools, go the Scripts Panel and then click this link: [begin test].

Perform the following steps, and note the expected results:

1. After clicking the link above, you should now be paused in the body of the test method, thanks to the `debugger` statement.

2. Add the following expressions to the "Watch Expressions" section of the Scripts panel sidebar pane: "`this`", "`a`", "`b`", "`c`" and "`d`". Do NOT enter the quotes.

3. The values of the expressions as shown in the window should be `Object` for `this`, `undefined` for the `a`, `b`, and `c` variables, and a value of `ReferenceError: d is not defined` for the `d` variable.

4. Note that the value for `d` should not change for the life of the test, as the variable `d` is never introduced in the program.

5. Step through the code, and you'll see the values of `a`, `b`, and `c` change, as the variables are assigned. Also note that as the scope changes due to the function invocation, values will be changed to refer to their current scope. The `this` expression will change when the method is invoked on the object constructed by the test.

6. Click different stack frames in the Call Stack section to ensure the expressions change value appropriately as the current stack frame changes.