[net] Subtract timestamps to determine if uploading file changed.

[net] Subtract timestamps to determine if uploading file changed.

UploadFileElementReader relies on checking the modified time of files
being uploaded to determine if a sliced file was modified during upload.
Clients of the net stack (in particular Blink) currently pass around the
expected modified time in a manner which cause the timestamp to lose
precision (E.g. converting to and from a double time_t).

As a result the expected timestamp and the current timestamp as returned
by GetFileInfo() will not match exactly. Current code attempted to
compensate for this by converting both timestamps to (integer) time_t.
However, since the conversion rounds down, this check would only succeed
if the loss of precision of the expected timestamp also caused it to
round down. This is not always the case. (E.g. (epoch + 10.999999) will
become 10 when converted to time_t, but the expected timestamp may have
rounded up to (epoch + 11.0) in the meantime.)

This patch compares the timestamps by checking if the magnitude of the
difference is less than one second.

BUG=426465
CQ_EXTRA_TRYBOTS=tryserver.blink:linux_blink_rel,linux_blink_dbg,mac_blink_rel,win_blink_rel
R=mmenke

Committed: https://crrev.com/b77c8ffae588001875fb50ead987a147ca882bdb
Cr-Commit-Position: refs/heads/master@{#314397}

Reverted: https://crrev.com/7ccf4fab5d4473e431f1a289056033eea0b3dd43
Cr-Commit-Position: refs/heads/master@{#314451}

Committed: https://crrev.com/91430c35820e73f2e388a94e8f6260be79e480a8
Cr-Commit-Position: refs/heads/master@{#314634}

[mmenke, 2015-02-02 15:34:21]

LGTM.  Also, in your description, checkinf -> checking

https://codereview.chromium.org/868253012/diff/1/net/base/upload_file_element...
File net/base/upload_file_element_reader_unittest.cc (right):

https://codereview.chromium.org/868253012/diff/1/net/base/upload_file_element...
net/base/upload_file_element_reader_unittest.cc:232:
expected_modification_time));
nit:  While you're here, should format the identical line in the above and below
tests to match this one, to make it clearer the tests are doing the exact same
thing here.

[asanka, 2015-02-03 19:22:32]

Thanks!

On 2015/02/02 at 15:34:21, mmenke wrote:
> LGTM.  Also, in your description, checkinf -> checking

Done.

> 
>
https://codereview.chromium.org/868253012/diff/1/net/base/upload_file_element...
> File net/base/upload_file_element_reader_unittest.cc (right):
> 
>
https://codereview.chromium.org/868253012/diff/1/net/base/upload_file_element...
> net/base/upload_file_element_reader_unittest.cc:232:
expected_modification_time));
> nit:  While you're here, should format the identical line in the above and
below tests to match this one, to make it clearer the tests are doing the exact
same thing here.

Done. But clang-format didn't want to format the WrongPath test identically to
the other two. It's close and is at least consistent with what clang-format
wants.

[asanka, 2015-02-03 19:22:39]

The CQ bit was checked by asanka@chromium.org

[commit-bot: I haz the power, 2015-02-03 19:23:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/868253012/20001

[mmenke, 2015-02-03 19:24:27]

On 2015/02/03 19:22:32, asanka wrote:
> Thanks!
> 
> On 2015/02/02 at 15:34:21, mmenke wrote:
> > LGTM.  Also, in your description, checkinf -> checking
> 
> Done.
> 
> > 
> >
>
https://codereview.chromium.org/868253012/diff/1/net/base/upload_file_element...
> > File net/base/upload_file_element_reader_unittest.cc (right):
> > 
> >
>
https://codereview.chromium.org/868253012/diff/1/net/base/upload_file_element...
> > net/base/upload_file_element_reader_unittest.cc:232:
> expected_modification_time));
> > nit:  While you're here, should format the identical line in the above and
> below tests to match this one, to make it clearer the tests are doing the
exact
> same thing here.
> 
> Done. But clang-format didn't want to format the WrongPath test identically to
> the other two. It's close and is at least consistent with what clang-format
> wants.

Ah, right...The last uses wrong_path.  Hadn't noticed that.  Still LGTM

[commit-bot: I haz the power, 2015-02-03 20:18:54]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-03 20:20:04]

Patchset 2 (id:??) landed as
https://crrev.com/b77c8ffae588001875fb50ead987a147ca882bdb
Cr-Commit-Position: refs/heads/master@{#314397}

[Noel Gordon, 2015-02-04 00:47:04]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/893323003/ by noel@chromium.org.

The reason for reverting is: Seems this made
http/tests/local/fileapi/send-sliced-dragged-file.html
fail the blink bots.

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#master=Ch...
.

[Noel Gordon, 2015-02-04 01:23:25]

When landing chromium changes via CQ, and you suspect might break something in
blink, add the following to your change description

CQ_EXTRA_TRYBOTS=tryserver.blink:linux_blink_rel,linux_blink_dbg

and so on for any blink-side bots you are worried about.  Failure in blink for
example from

https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Linux/436...

was 
https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Linux/436...

PASS subfile.size is 5
PASS subfile.type is ""
PASS Expected response data received: OK
PASS Expected exception thrown: NetworkError
FAIL Unexpected response data received: OK. Expecting exception thrown

[asanka, 2015-02-04 19:43:39]

On 2015/02/04 at 01:23:25, noel wrote:
> When landing chromium changes via CQ, and you suspect might break something in
blink, add the following to your change description
> 
> CQ_EXTRA_TRYBOTS=tryserver.blink:linux_blink_rel,linux_blink_dbg
> 
> and so on for any blink-side bots you are worried about.  Failure in blink for
example from
> 
>
https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Linux/436...
> 
> was 
https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Linux/436...
> 
> PASS subfile.size is 5
> PASS subfile.type is ""
> PASS Expected response data received: OK
> PASS Expected exception thrown: NetworkError
> FAIL Unexpected response data received: OK. Expecting exception thrown

Looks like the blink try jobs are succeeding with the fix to the layout tests.

The layout tests were also implicitly relying on time stamp conversion to time_t
always rounding down, which is the assumption being corrected in this patch.
There are no code changes between the patchset originally committed and the one
I'm about to put on the CQ.

[asanka, 2015-02-04 19:44:58]

The CQ bit was checked by asanka@chromium.org

[commit-bot: I haz the power, 2015-02-04 19:46:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/868253012/20001

[commit-bot: I haz the power, 2015-02-04 21:13:50]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-04 21:15:49]

Patchset 2 (id:??) landed as
https://crrev.com/91430c35820e73f2e388a94e8f6260be79e480a8
Cr-Commit-Position: refs/heads/master@{#314634}