Handle if the printing app is killed while saving to PDF.

When saving to PDF we bring up the file picker UI which covers
the print UI. In this case the printing app may get killed as
it is not in the forground (the system is bound to the print
spooler so it cannot get killed). If that happens we are ending
up with an empty file. However, if the file chooser UI is up
we already have everything from the app we need and it dying
does not matter. This change takes care if ignoring printing
app death while saving to PDF.

bug:17922948

Change-Id: I10d808e3c3e93e850dbc2a948f2482381a887928