The current version of go/printer formats the following code
like this:

	foo.Bar().
		Run(func() {
		do()
	}).
		Set(map[string]interface{}{
		"x": "three",
		"y": 4,
	}).
		Run(
		func() {
			do()
		},
	)

This CL changes the go/printer behaviour to make the code look
like this.

	foo.Bar().
		Run(func() {
			do()
		}).
		Set(map[string]interface{}{
			"x": "three",
			"y": 4,
		}).
		Run(
			func() {
				do()
			},
		)

Fixes #12066.

Change-Id: If0f525dae1a5d45f9ba40534dbb65715d7e8001b
Reviewed-on: https://go-review.googlesource.com/13928Reviewed-by: Robert Griesemer <gri@golang.org>