Do not cache an IOBuffer in AsyncResourceHandler if data_ is NULL.

CHECK that IOBuffer::data_ in AsyncResourceHandler is not NULL before caching it.
BUG=http://crbug.com/16371

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=22214

[willchan no longer on Chromium, 2009-07-31 21:29:42]

http://code.google.com/p/chromium/issues/detail?id=17363 has an example of a
user hitting
[6073:6078:165451373342:FATAL:/b/slave/chrome-official-linux/build/src/chrome/browser/renderer_host/async_resource_handler.cc(86)]
Check failed: read_buffer_->data().

I'm not sure why data is NULL at this case, but if it is NULL, we shouldn't
cache it.

[rvargas (doing something else), 2009-07-31 21:54:56]

http://codereview.chromium.org/159730/diff/1/2
File chrome/browser/renderer_host/async_resource_handler.cc (right):

http://codereview.chromium.org/159730/diff/1/2#newcode145
Line 145: NOTREACHED() << "http://crbug.com/16371";
I think we actually have to crash here too. As far as I can see, we should never
have a read_buffer_ without data because that somehow implies that the
destructor of the buffer already run but we still have a pointer to it.

[willchan no longer on Chromium, 2009-07-31 22:04:53]

Switched to CHECK and updated the description.

[rvargas (doing something else), 2009-07-31 22:06:53]

LGTM