Get rid of the dependency on WebKit::WebCursorInfo internals from WebCursor.

      This will help ensure that we don't have to depend on WebKit when we use the WebCursor
class. The current consumers of this class are plugins and browser.

We still have a dependency on the WebCursorInfo::Type enum which is fine. 

Added helper functions InitializeCursorFromWebKitCursorInfo  and GetWebKitCursorInfo to the webkit_glue
namespace in the newly added cursor_utils.cc/.h files which live in webkit_glue. These functions adapt
WebCursorInfo to our WebCursor and vice versa.

With this change we can move the WebCursor class to webkit\common in a subsequent CL.

BUG=237249
TBR=jamesr@chromium.org

Review URL: https://codereview.chromium.org/15946004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202220 0039d316-1c4b-4281-b951-d872f2087c98