Save Breakpad symbol files for main executable name variants

Save Breakpad symbol files for main executable name variants.

This allows symbolization of Google Chrome Canary, Google Chrome Helper EH,
and Google Chrome Helper NP. The practical effect of this is that _main and
start will be properly symbolized by Breakpad.

BUG=94540
TEST=Look at the Breakpad crash reports for the canary browser process,
     plug-in process, and NaCl loader process. The bottom of each stack should
     show ChromeMain being called by main, which is in turn called by start.
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=98682

[TVL, 2011-08-29 20:00:41]

lgtm