Remove app_shell chrome.shell API and ShellAppWindow
The chrome.app.window API has been moved to src/extensions, so app_shell
no longer needs its custom chrome.shell API to open windows.
* Remove the API implementation -- mostly a manual revert of https://codereview.chromium.org/
254473011/
* Remove app_shell_resources.grd since there are no more app_shell resources
* Remove athena's support for ShellAppWindow
* Fix example apps to remove the chrome.shell workaround.
No presubmit because it has a false-positive warning about the enum rename in extension_function_histogram_value.h
No try because no presubmit doesn't seem to work by itself.
BUG=413164
TEST=extensions_unittests, app_shell_unittests, app_shell_browsertests
TBR=isherman@chromium.org for deprecating an extension function histogram
NOPRESUBMIT=true
NOTRY=true
Review URL: https://codereview.chromium.org/
571643003
Cr-Commit-Position: refs/heads/master@{#294852}