Add instrumentation to track down a crash....

Add instrumentation to track down a crash.

Promotes some DCHECKs to CHECKs, to figure out who is calling URLFetcher::Start() without having first set a valid request context.

Also adds a |was_cancelled_| variable to rule out that Start() isn't called after the request was already cancelled.

This change can be reverted once we get the data.

BUG=27074
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=31526

[wtc, 2009-11-10 00:53:06]

LGTM.

http://codereview.chromium.org/377041/diff/1/2
File chrome/browser/net/url_fetcher.cc (right):

http://codereview.chromium.org/377041/diff/1/2#newcode98
Line 98: // Temporary variable to test a crash theory.
Nit: variable => member or member variable

Although this member is temporary, you should still describe
what it is.

[eroman, 2009-11-10 01:00:31]

http://codereview.chromium.org/377041/diff/1/2
File chrome/browser/net/url_fetcher.cc (right):

http://codereview.chromium.org/377041/diff/1/2#newcode98
Line 98: // Temporary variable to test a crash theory.
On 2009/11/10 00:53:06, wtc wrote:
> Nit: variable => member or member variable
> 
> Although this member is temporary, you should still describe
> what it is.
> 
> 

Done. 

Reworded to:

  // Temporary member variable to test whether requests are being started
  // after they have already been cancelled.

[wtc, 2009-11-10 01:09:25]

http://codereview.chromium.org/377041/diff/2002/2003
File chrome/browser/net/url_fetcher.cc (right):

http://codereview.chromium.org/377041/diff/2002/2003#newcode101
Line 101: bool was_cancelled_;
You explained what this member is for, but you should also
describe what it is.
  True if the request has been cancelled.
or
  True if CancelURLRequest has been called.