Another attempt to fix a Chrome crash.

Another attempt to fix a Chrome crash.

From the bug report and the other relevant bug 236392 reported by ASan,
The problem arises when ReadData() had some errors or completed, and then freed
the NetworkStats, but later the callback of the Write() is started on the freed
object. This most likely happened when the initial ReadData() had some errors.
So I did two modifications.
1. For the first time when ReadData is called, I checked the return value.
Only if it is ERR_IO_PENDING, it continues to Send requests.
2. The Write() callback is on a WeakPtr. If the NetworkStats object is freed,
the callback will be a no-op.

BUG=273917
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=221644

[honghaiz, 2013-09-04 18:46:20]

On 2013/09/03 18:19:48, honghaiz wrote:

Ping for code review.

[honghaiz, 2013-09-05 17:23:35]

I hope to get the fix into the canary before the weekend. 
Can you provide the code review today?

[jar (doing other things), 2013-09-05 21:17:11]

lgtm

[commit-bot: I haz the power, 2013-09-05 21:35:44]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/honghaiz@chromium.org/23875004/1

[commit-bot: I haz the power, 2013-09-06 08:21:40]

Change committed as 221644