goobspatch: Improve sanity checks for invalid patches.

goobspatch: Improve sanity checks for invalid patches.

This patch checks that the length passed to cfread() is non
negative. The individual read methods on cfread() check for failure
while reading a negative value, but the actual failure is a malformed
patch.

R=mark@chromium.org
BUG=chromium:372525
TEST=Manually run a local bad patch and check it fails with the new message.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269935

[Mark Mentovai, 2014-05-12 19:57:47]

Great catch!

[Mark Mentovai, 2014-05-12 19:57:51]

LGTM

[deymo, 2014-05-12 20:15:02]

The CQ bit was checked by deymo@chromium.org

[commit-bot: I haz the power, 2014-05-12 20:15:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/deymo@chromium.org/287483002/1

[commit-bot: I haz the power, 2014-05-13 00:19:39]

Change committed as 269935