Update CoreBrowserService.ts

[frost-cy]

Move the initializer into the constructor for instance members that reference identifiers declared in the constructor.

When TypeScript outputs modern language features, the below case throws an TS error.

class C {
  a = this.x; // TS2729: Property 'x' is used before its initialization. 

  constructor(public x:number){}
}

This error is fixed by moving the initializer of such class members into the constructor.

This is a no-op change