UsbDeviceHandleImpl must hold a scoped_refptr to UsbDeviceImpl.

UsbDeviceHandleImpl must hold a scoped_refptr to UsbDeviceImpl.

When a USB device is disconnected the last reference to the UsbDevice
object representing it may be freed. Outstanding device handles should
retain a reference to the UsbDevice object until they themselves are
closed (which is done in UsbDeviceImpl::OnDisconnect). This call
releases the circular reference between UsbDeviceImpl and its open
UsbDeviceHandleImpl children.

Otherwise the UsbDeviceImpl will outlive the UsbDeviceHandleImpl and
UsbDeviceHandleImpl::GetDevice will attempt to call AddRef on an invalid
pointer.

BUG=447761
Committed: https://crrev.com/e1a9120d381ae6c12535ea8b2c5679700320398a
Cr-Commit-Position: refs/heads/master@{#310907}

[Reilly Grant (use Gerrit), 2015-01-09 22:31:11]

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

[Reilly Grant (use Gerrit), 2015-01-09 23:15:32]

Bare pointers to refcounted objects FTW!

[Ken Rockot(use gerrit already), 2015-01-09 23:36:08]

lgtm

[Reilly Grant (use Gerrit), 2015-01-10 00:07:51]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2015-01-10 00:09:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/835313003/1

[commit-bot: I haz the power, 2015-01-10 00:14:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-10 00:15:04]

Patchset 1 (id:??) landed as
https://crrev.com/e1a9120d381ae6c12535ea8b2c5679700320398a
Cr-Commit-Position: refs/heads/master@{#310907}