Add StackTrace::ToString().

Add StackTrace::ToString().

This can be used for debug logging like:

  LOG(ERROR) << base::debug::StackTrace().ToString();

As opposed to

  std::strstream stream;
  base::debug::StackTrace().OutputToStream(&stream);
  LOG(ERROR) << stream.str();

BUG=none
TEST=add a test to stack_unitttest and confirm it passes


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=105085

[satorux1, 2011-10-12 05:24:48]

Ping. I thought it's a good change. Streams are discouraged by the C++ style
guide, and this change allows you to use this class without introducing extra
stream objects like std::strstream mentioned in the description. Please let me
know if you don't feel like reviewing the patch, or just don't like the patch.
:)

[willchan no longer on Chromium, 2011-10-12 05:30:48]

LGTM, sorry, was just slow.

[commit-bot: I haz the power, 2011-10-12 14:51:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/satorux@chromium.org/8206015/1

[commit-bot: I haz the power, 2011-10-12 16:13:41]

Change committed as 105085