Implement direction-specific touch-action values.
Add PanLeft, PanRight, PanUp and PanDown support by generalizing the PanX and PanY code.
The fix for the bug is a 3 part change and is required
because of the dependencies of blink as there is a static
cast (causing a ABI dependency). To work around this ABI
problem this is part 1 adding the PanXXX definitions to the
content classes and disabling the static assertions and
casting. The second change is
https://codereview.chromium.org/
1137483003/. Once that
change has landed a follow up change to this change one
will remove the #if 0 and re-add the static cast between
blink::WebTouchAction and content::TouchAction
BUG=476556
TEST=content_unittests
Review URL: https://codereview.chromium.org/
1131093002
Cr-Commit-Position: refs/heads/master@{#329011}