Refactor taskbar anchoring tests on Windows to match Mac tests.
This affects both AppListWinUnitTest and AppListPositionerUnitTest. It
now uses named constants and expressions instead of hard-coded numbers
in the tests. It also uses abstractions to set up state rather than
manually supplying the parameters in each test case.
Also moved app_list_win's FindAnchorPoint into the AppListWin class.
BUG=317944
Review URL: https://codereview.chromium.org/
80053003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236676 0039d316-1c4b-4281-b951-d872f2087c98