Override base::FILE_EXE in ContentMainDelegateQt::PreSandboxStartup()
with the path to our child process and get rid of the command line
argument and the content::CHILD_PROCESS_EXE override.
This reduces 0001-My-local-fixes.patch to export ContentMainRunner
so the patch can be renamed to better reflect it's purpose.
This hunk is still needed since we need to access ContentMainRunner's
Initialize() to set our ContentMainDelegate.

Change-Id: I808cb114100300a33f8cb1b154c6cde89cbf5d98
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>