EXO: Change surface includes

Remove pointer.h include and replace with wm_helper.h include.
pointer.h is not needed, but wm_helper is needed as it was transitively
included through pointer.h.

Bug: 896710
Test: Built on ChromeOS
Change-Id: Ic3dea290b4662cc5d868e7568c4909257dd55122
Reviewed-on: https://chromium-review.googlesource.com/c/1324749Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Shawn Gallea <sagallea@google.com>
Cr-Commit-Position: refs/heads/master@{#606594}

components/exo/surface.cc

@@ -15,9 +15,9 @@
 #include "base/trace_event/traced_value.h"
 #include "cc/trees/layer_tree_frame_sink.h"
 #include "components/exo/buffer.h"
-#include "components/exo/pointer.h"
 #include "components/exo/surface_delegate.h"
 #include "components/exo/surface_observer.h"
+#include "components/exo/wm_helper.h"
 #include "components/viz/common/quads/render_pass.h"
 #include "components/viz/common/quads/shared_quad_state.h"
 #include "components/viz/common/quads/solid_color_draw_quad.h"