Fix a DCHECK that could fire in PassiveLogCollector for a particular stream o...

Fix a DCHECK that could fire in PassiveLogCollector for a particular stream of events.

The sequence of events needed to trigger the assertion is a little complicated (see unittest for specifics).

The general pattern goes something like this:
  (1) Add a dependency between two sources of different types. (This increments the refcount on the dependency.)
  (2) Saturate the "graveyard" containing the dependency causing it to be nuked.
  (3) Add a new entry to the original dependency, causing it to re-create the source (but now with 0 refcount).
  (4) Force the buffer containing the source in step (1) to be nuked
  (5) In releasing the dependencies, it will now try to release reference on non-existent source.

While this was crashing debug mode, I don't believe there would have been an impact on release builds (since DeleteSourceInfo() early returns if it can't find the source).

BUG=58847
TEST=PassiveLogCollectorTest.ReleaseDependencyToUnreferencedSource
  

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=66147

[mmenke, 2010-11-15 16:21:52]

LGTM.

Doesn't look like it would have caused issues in release builds to me, either.

http://codereview.chromium.org/4960001/diff/1/chrome/browser/net/passive_log_...
File chrome/browser/net/passive_log_collector_unittest.cc (right):

http://codereview.chromium.org/4960001/diff/1/chrome/browser/net/passive_log_...
chrome/browser/net/passive_log_collector_unittest.cc:443: PassiveLogCollector x;
nit:  You're undoubtedly more familiar with Google style guidelines than I, but
you might want to give this a better name.  Would make lines longer and a little
messier, though, so maybe not.

[eroman, 2010-11-15 19:28:10]

http://codereview.chromium.org/4960001/diff/1/chrome/browser/net/passive_log_...
File chrome/browser/net/passive_log_collector_unittest.cc (right):

http://codereview.chromium.org/4960001/diff/1/chrome/browser/net/passive_log_...
chrome/browser/net/passive_log_collector_unittest.cc:443: PassiveLogCollector x;
On 2010/11/15 16:21:52, Matt Menke wrote:
> nit:  You're undoubtedly more familiar with Google style guidelines than I,
but
> you might want to give this a better name.  Would make lines longer and a
little
> messier, though, so maybe not.

Done.

You are right, |x| is a bad name. (carry over from some test code I had).

I have renamed it to |log| to be consistent with the other tests in this file.