How is a context in Android created? What is the purpose of ContextThemeWrapper?

Question

I'm helping put together this page: What is a context?

To help illustrate how components are related to a Context, I created this diagram from looking through the framework source code:

After digging around a bit, I had the following questions:

1. What creates a Context and what concrete classes are used? The base Context class itself is an abstract class, which requires almost all of its methods to be implemented. And a ContextWrapper, when instantiated, requires a Context instance to be passed in as it's base context, so there must be at least one concrete Context class.
2. I understand that the ContextWrapper and its subclasses utilize the wrapper/decorator pattern to add functionality to the base Context class as needed. What is the purpose of the ContextThemeWrapper? It overrides a few methods, but if it's wrapping a base Context, why not just delegate the calls to the base Context? For example, the Activity class extends ContextThemeWrapper, which provides a specific implementation for getTheme() and setTheme(). Why?

The Android developer java docs are a bit vague. E.g., ContextWrapper

Answer 1

Answering #2:

ContextThemeWrapper adds theming support to a Context, otherwise you can't apply any theme to the Views you create. That's why Activity layouts support themes while widget layouts don't, for example. You can also create a ContextThemeWrapper yourself to override the current theme with another one.