**Do you want to request a *feature* or report a *bug*?**

bug

**What is the current behavior?**

The warning for a failure to initialize state when using `getDerivedStateFromProps` is not as clear as it could be.

This component produces the warning:
> MyComponent: Did not properly initialize state during construction. Expected state to be an object, but it was undefined.`

```js
class MyComponent extends React.Component {
  static getDerivedStateFromProps(nextProps, prevState) {
    return null;
  }
  render() {
    return <span>Foo</span>
  }
}
```

The warning can be resolved by adding `state = {}` either in the class definition or the constructor, or by not using `getDerivedStateFromProps`.

See https://github.com/reactjs/reactjs.org/issues/796 for more detail on why this warning message can be counter-intuitive.

Since the [warning is specific](https://github.com/facebook/react/blob/b548b3cd640dbd515f5d67dafc0216bb7ee0d796/packages/react-reconciler/src/ReactFiberClassComponent.js#L509-L510) to the use of `getDerivedStateFromProps` and not triggered by any other state or lifecycle methods, and state initialization isn't required for other state methods like `this.setState`, it would make sense to me to mention `getDerivedStateFromProps` explicitly in the warning.

Here's a proposal for a new warning message:
> MyComponent: Component state must be initialized when using getDerivedStateFromProps. Expected state to be an object, but it was undefined.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

React >= 16.3.0

((topFrame: any): FrameDev).debugElementStack = [];
    }
    this.stack = [topFrame];
    this.exhausted = false;
    this.currentSelectValue = null;
    this.previousWasTextNode = false;
    this.makeStaticMarkup = makeStaticMarkup;
    // Context (new API)
    this.contextIndex = -1;
    this.contextStack = [];
    this.contextValueStack = [];
    if (__DEV__) {
      this.contextProviderStack = [];
    }
  }
  /**
   * Note: We use just two stacks regardless of how many context providers you have.
   * Providers are always popped in the reverse order to how they were pushed
   * so we always know on the way down which provider you'll encounter next on the way up.
   * On the way down, we push the current provider, and its context value *before*
   * we mutated it, onto the stacks. Therefore, on the way up, we always know which
   * provider needs to be "restored" to which value.
   * https://github.com/facebook/react/pull/12985#issuecomment-396301248
   */
  pushProvider<T>(provider: ReactProvider<T>): void {
    const index = ++this.contextIndex;
    const context: ReactContext<any> = provider.type._context;
    const previousValue = context._currentValue;
    
    this.contextStack[index] = context;