[WebMIDI] Introduce UsbMidi{Input, Output}Stream.

UsbMidiInputStream converts USB-MIDI messages to MIDI messages.
UsbMidiOutputStream converts MIDI MIDI messages to USB-MIDI messages.

BUG=303596
R=toyoshim@chromium.org

Review URL: https://codereview.chromium.org/107513012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246277 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246277
Support relative file paths in FilePathToFileURL().

This makes it possible for content_shell to resolve relative file paths
on the command line and turn them into proper startup URLs.

BUG=336416

Review URL: https://codereview.chromium.org/137233006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246278 0039d316-1c4b-4281-b951-d872f2087c98
* Make AttemptExit/AttemptRestart do the right thing on chromeos
 AttemptExit now simply calls AttemptUserExit. They're the same on ChromeOS.
 AttemptRestart simply exists so that the session manager will restart the chrome.

* Don't use ExitCleanly to restart the browser, as this is meant for SIGTERM.

* Minior cleanup: rename g_session_manager_requested_shutdown to g_send_stop_request_to_sesion_manager.

BUG=335195

Review URL: https://codereview.chromium.org/141143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246279 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246279
Make GetDefaultThreadStackSize() return 16M under ThreadSanitizer
This should help some browser tests that are currently hitting the roof under TSan.

BUG=335516
R=epenner@chromium.org,dvyukov@chromium.org

Review URL: https://codereview.chromium.org/143933002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246280 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246280