[unbound-method] rule triggered when binding a class method

[andsouto]

Repro

{
  "rules": {
    "@typescript-eslint/unbound-method": ["error"]
  }
}

class Foo {
	constructor() {
		this.onMessage = this.onMessage.bind(this);
	}

	onMessage(): void {}
}

Expected Result
No error detected

Actual Result
Avoid referencing unbound methods which may cause unintentional scoping of this @typescript-eslint/unbound-method

Additional Info
As far as I know this is a common pattern for binding event handlers. Could be related with #692

Versions

package	version
@typescript-eslint/eslint-plugin	1.11.0
@typescript-eslint/parser	1.11.0
TypeScript	3.5.3
ESLint	5.16.0
node	8.16.0
npm	6.10.0

[glen-84]

Is this a duplicate of #636?