compositing: Implement cursor per CSS3-UI § 8.1.1 in the CEF/Mac port.

I'm not sure how we want to handle Linux cursors, and GLFW has no
ability to set cursors (short of disabling it and managing it yourself).

components/util/cursor.rs

@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! A list of common mouse cursors per CSS3-UI § 8.1.1.
+
+#[deriving(Clone, PartialEq, FromPrimitive, Show)]
+#[repr(u8)]
+pub enum Cursor {
+    NoCursor = 0,
+    DefaultCursor = 1,
+    PointerCursor = 2,
+    ContextMenuCursor = 3,
+    HelpCursor = 4,
+    ProgressCursor = 5,
+    WaitCursor = 6,
+    CellCursor = 7,
+    CrosshairCursor = 8,
+    TextCursor = 9,
+    VerticalTextCursor = 10,
+    AliasCursor = 11,
+    CopyCursor = 12,
+    MoveCursor = 13,
+    NoDropCursor = 14,
+    NotAllowedCursor = 15,
+    GrabCursor = 16,
+    GrabbingCursor = 17,
+    EResizeCursor = 18,
+    NResizeCursor = 19,
+    NeResizeCursor = 20,
+    NwResizeCursor = 21,
+    SResizeCursor = 22,
+    SeResizeCursor = 23,
+    SwResizeCursor = 24,
+    WResizeCursor = 25,
+    EwResizeCursor = 26,
+    NsResizeCursor = 27,
+    NeswResizeCursor = 28,
+    NwseResizeCursor = 29,
+    ColResizeCursor = 30,
+    RowResizeCursor = 31,
+    AllScrollCursor = 32,
+    ZoomInCursor = 33,
+    ZoomOutCursor = 34,
+}
+