If a user requests a try on "all" builders, ask for confirmation

If a user requests a try on "all" builders, ask for confirmation

Addresses https://code.google.com/p/skia/issues/detail?id=1208
(SkipBuildbotRuns)

R=epoger@google.com

Committed: https://code.google.com/p/skia/source/detail?r=10049

[borenet, 2013-07-09 20:36:11]

Is this sufficient to cover https://code.google.com/p/skia/issues/detail?id=1208
?
I think that if a user takes the time to type out a "large" number of bots, they
probably want all of them, whereas "all" is something that can be more lazily
done.

https://codereview.chromium.org/18190006/diff/1/tools/submit_try
File tools/submit_try (right):

https://codereview.chromium.org/18190006/diff/1/tools/submit_try#newcode217
tools/submit_try:217: using_bots = [t for t in trybots if t.startswith('Build')]
Unfortunately, this didn't get changed after the builder name change.

[epoger, 2013-07-12 15:13:30]

lgtm

[borenet, 2013-07-12 18:11:11]

Committed patchset #1 manually as r10049 (presubmit successful).