window.print() should close form validation bubble.

Usually, window.open() deactivates the origin window and validation bubble on the
origin window is closed. However, if window.print() is executed, it suspends message
loop of the window, and deactivation isn't noticed until print dialog is closed.
So, we need to close validation popup explicitly for window.print().

BUG=713686

Review-Url: https://codereview.chromium.org/2834783002
Cr-Commit-Position: refs/heads/master@{#466273}
4 files changed