Browser: Extract out timeout handling

[inancgumus]

What

Handle timeout settings in a dedicated piece of code.

Why

We currently set timeouts like this:

// timeouts must be multiplied by milliseconds
..timeout = time.Duration(obj.Get(k).ToInteger()) * time.Millisecond

We repeat from multiple places in the code. It's error-prone, and we must remember to do this every time.

How

Add a dedicated package or function to handle timeout calculations.