support content_shell

chromium content_shell for linux uses different version string.
the string is fixed and not changed automatically in content_shell.gypi.
('content_shell_version': '19.77.34.5')
trace-viewer checks the chrome version from UA whether the browser
is higher than 36. This CL makes trace-viewer check content_shell_version too.

BUG=674
okay, I misunderstood your intention.
if you see the comment in content_shell.gypi, it shows the version meaning.
the "19" is the major version at the patch had been landed.
the last numbers("77.34.5") give a hint that the binary is not ordinary chrome(content_shell).
so I think it is enough to check "77.34.5" in the version string.

var support_content_shell = window.navigator.appVersion.match("77.34.5");
if (ver < 36 && !support_content_shell)

we can not distinguish whether the content_shell is higher than 36.
because content_shell had been using the same version since 2012.
if in future content_shell increases the version, that would be like "20.77.34.5".