Pepper: Simplify LaunchSelLdr error reporting.

This moves error reporting for LaunchSelLdr out of the trusted plugin, removing
the need for a callback in ServiceRuntime to unpack the error string and report
it.

This is part of a larger effort to move all code out of the trusted plugin.

BUG=239656
R=bbudge@chromium.org

Review URL: https://codereview.chromium.org/282683002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270140 0039d316-1c4b-4281-b951-d872f2087c98
11 files changed