Measure content view with spec mode EXACTLY.

It's usual for a top view in our activity's hierarchy to expect being measured with spec mode `EXACTLY`.
To illustrate, `DrawerLayout` provided by Android support library requires to measured with this spec.
And it's common practice to make this layout be a top view with `MATCH_PARENT` value for layout width and height.

This commit also renames `TestWindowTest` to `WindowTest` since the tests were being excluded before, though all the tests in that class pass (there are also `TestMenuTest` and `TestMenuItemTest` classes, but I haven't taken a look at them).