Refactor SnapSizer now that the --ash-multiple-snap-window-widths flag no longer exists

Notable changes:
Removes the window snapping functionality out of SnapSizer
Introduce SnapSizer::SnapLeftWithDefaultWidth()
          SnapSizer::SnapRightWithDefaultWidth()
          wm::GetLeftSnappedWindowBoundsInParent()
          wm::GetRightSnappedWindowBoundsInParent()

Rename SnapSizer to TwoStepEdgeCycler and strip it down as much as possible. In a future CL I will clean up WorkspaceWindowResizer's use of TwoStepEdgeCycler.

BUG=343276

Review URL: https://codereview.chromium.org/178573002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253434 0039d316-1c4b-4281-b951-d872f2087c98
Remove WebRTC.AudioOutputChannelLayout UMA histogram and mark it obsolete.

We hard code the value to stereo today, and the resampler will do
up/down-mixing if the native channel layout is different from stereo.

BUG=none

Review URL: https://codereview.chromium.org/177213011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253435 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253435
Add a new "--start-fullscreen" command line switch to change the window to fullscreen on start, just like if the user had pressed F11 right after startup.

This is different from the already existing "--kiosk" mode, where the user can't get out of fullscreen mode.

Being able to start the browser in fullscreen mode and getting out of it afterwards on demand is interesting if the user wants to use Chromium for system monitoring on embedded systems, but wants to exit fullscreen occasionally if required.

The call to chrome::ToggleFullScreenMode() in StartupBrowserCreatorImpl::OpenTabsInBrowser() has to be done after the window is shown. This patch is a good opportunity to fix this problem for kiosk mode too, because currently it's not working on Linux because chrome::ToggleFullScreenMode() is called before the window is shown.

BUG=167430

Review URL: https://codereview.chromium.org/175733002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253436 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253436