Add utilities to parse WebUSB device descriptors.

Add utilities to parse WebUSB device descriptors.

These structs and methods will be used to parse the WebUSB descriptors
on compatible devices as part of the enumeration process. Tests are
provided for example descriptors and a number of various corrupt cases.

BUG=492204
Committed: https://crrev.com/d80d79b21fbad4eb834f154660dcdca3720f5622
Cr-Commit-Position: refs/heads/master@{#341959}

[Reilly Grant (use Gerrit), 2015-08-03 23:22:30]

reillyg@chromium.org changed reviewers:
+ rockot@chromium.org

[Reilly Grant (use Gerrit), 2015-08-03 23:22:30]

Please take a look.

[Ken Rockot(use gerrit already), 2015-08-04 00:59:02]

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
File device/usb/webusb_descriptors.cc (right):

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
device/usb/webusb_descriptors.cc:38: DCHECK_EQ((*it)[1], kUrlDescriptorType);
If it is passed as 1 short of |end|, can't (*it)[1] be out of bounds?

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
device/usb/webusb_descriptors.cc:40: const char* str = reinterpret_cast<const
char*>(&(*it)[2]);
As can (*it)[2]

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
device/usb/webusb_descriptors.cc:41: *url = GURL(std::string(str, length - 2));
length - 2 can underflow

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
device/usb/webusb_descriptors.cc:55: DCHECK_EQ((*it)[1],
kFunctionSubsetDescriptorType);
same deal as above

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
device/usb/webusb_descriptors.cc:167: return false;
Is it worth vlogging anything for some of these failure modes?

[Reilly Grant (use Gerrit), 2015-08-04 01:05:20]

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
File device/usb/webusb_descriptors.cc (right):

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
device/usb/webusb_descriptors.cc:38: DCHECK_EQ((*it)[1], kUrlDescriptorType);
On 2015/08/04 00:59:02, Ken Rockot wrote:
> If it is passed as 1 short of |end|, can't (*it)[1] be out of bounds?

These properties should be guaranteed by the caller which is why they are
DCHECKs here. That said, the empty string case is interesting so I'll add a test
and more DCHECKs.

https://codereview.chromium.org/1256113006/diff/1/device/usb/webusb_descripto...
device/usb/webusb_descriptors.cc:167: return false;
On 2015/08/04 00:59:02, Ken Rockot wrote:
> Is it worth vlogging anything for some of these failure modes?

I had a bunch of VLOGs when I was developing but I'm not sure how useful they
will be in production. I'd rather not dump a bunch of data from this low in the
library. I would rather have a separate application for viewing/validating
descriptors for developers.

[Reilly Grant (use Gerrit), 2015-08-04 20:47:31]

Please take another look.

[Ken Rockot(use gerrit already), 2015-08-05 14:16:56]

lgtm

https://codereview.chromium.org/1256113006/diff/20001/device/usb/webusb_descr...
File device/usb/webusb_descriptors.cc (right):

https://codereview.chromium.org/1256113006/diff/20001/device/usb/webusb_descr...
device/usb/webusb_descriptors.cc:34: std::vector<uint8_t>::const_iterator* it,
in these functions |it| is an input and output argument. Style guide calls for
output arguments to come last. I'm not sure it makes sense to apply that rule
here, but please consider it.

https://codereview.chromium.org/1256113006/diff/20001/device/usb/webusb_descr...
device/usb/webusb_descriptors.cc:36: // These statements must be guaranteed by
the caller.
Suggestion: statements -> conditions?

[Reilly Grant (use Gerrit), 2015-08-05 16:31:56]

https://codereview.chromium.org/1256113006/diff/20001/device/usb/webusb_descr...
File device/usb/webusb_descriptors.cc (right):

https://codereview.chromium.org/1256113006/diff/20001/device/usb/webusb_descr...
device/usb/webusb_descriptors.cc:34: std::vector<uint8_t>::const_iterator* it,
On 2015/08/05 14:16:56, Ken Rockot wrote:
> in these functions |it| is an input and output argument. Style guide calls for
> output arguments to come last. I'm not sure it makes sense to apply that rule
> here, but please consider it.

Considered. Passing end, begin is weirder than passing an out parameter as the
first argument.

https://codereview.chromium.org/1256113006/diff/20001/device/usb/webusb_descr...
device/usb/webusb_descriptors.cc:36: // These statements must be guaranteed by
the caller.
On 2015/08/05 14:16:56, Ken Rockot wrote:
> Suggestion: statements -> conditions?

Done.

[Reilly Grant (use Gerrit), 2015-08-05 16:34:16]

The CQ bit was checked by reillyg@chromium.org

[Reilly Grant (use Gerrit), 2015-08-05 16:34:16]

The patchset sent to the CQ was uploaded after l-g-t-m from rockot@chromium.org
Link to the patchset: https://codereview.chromium.org/1256113006/#ps40001
(title: "Comment tweaks.")

[commit-bot: I haz the power, 2015-08-05 16:34:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1256113006/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1256113006/40001

[commit-bot: I haz the power, 2015-08-05 17:05:14]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-05 17:05:15]

Try jobs failed on following builders:
  linux_chromium_chromeos_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Reilly Grant (use Gerrit), 2015-08-05 18:10:33]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2015-08-05 18:11:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1256113006/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1256113006/40001

[commit-bot: I haz the power, 2015-08-05 20:27:19]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-08-05 20:28:04]

Patchset 3 (id:??) landed as
https://crrev.com/d80d79b21fbad4eb834f154660dcdca3720f5622
Cr-Commit-Position: refs/heads/master@{#341959}