Fix DualMode ShellIntegrationWin tests on Win10.
Fix DualMode ShellIntegrationWin tests on Win10.

Also adding one more test case.

BUG=514331
TEST=Run unit_tests.exe --gtest_filter=*ShellInt*Dual* on Win8 once and a second time
with InstallUtil::ShouldInstallMetroProperties() locally tweaked to < VERSION_WIN8,
passes both ways.
R=grt@chromium.org

Review URL: https://codereview.chromium.org/1255303003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#340950}

CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,CapOM/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend,ltilve/ChromiumGStreamerBackend