Make the snap left and snap right buttons snap a window to the correct side when using the right-to-left layout 
and the --ash-enable-alternate-caption-button command line flag

BUG=340141
TEST=AlternateFrameSizeButtonTestRTL.ButtonDrag

Review URL: https://codereview.chromium.org/152353002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253968 0039d316-1c4b-4281-b951-d872f2087c98
Do more slash normalization in GN.

This makes GN more aggressive about converting backslashes into forward-slashes, and makes the path handling functions mostly indifferent with regard to the two types of slashes.

The previous behavior was a bit confusing in that you would end up with strings like "//out\Debug/" on Windows, and certain operations on this would fail. With this change, the backslash will be more aggressively converted. The downside is that Posix filenames with literal backslashes in them are now unrepresentable in GN. But I think for a cross-platform system on constrained input (build files) this is a reasonable tradeoff for more consistent path handling.

R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/177003008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253969 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253969