ozone: Introduce ClientPixmap and ClientPixmapFactory for non-GPU processes.

ui/ozone/public/overlay_candidates_ozone.h

Index: ui/ozone/public/overlay_candidates_ozone.h
diff --git a/ui/ozone/public/overlay_candidates_ozone.h b/ui/ozone/public/overlay_candidates_ozone.h
index e71dc6f22b39c7cd8ed3092cd34b2e6ee4f6bb7e..3828955f94be0666ea543e79d501b405ba35e233 100644
--- a/ui/ozone/public/overlay_candidates_ozone.h
+++ b/ui/ozone/public/overlay_candidates_ozone.h
@@ -26,7 +26,7 @@ class OZONE_BASE_EXPORT OverlayCandidatesOzone {
     // Transformation to apply to layer during composition.
     gfx::OverlayTransform transform = gfx::OVERLAY_TRANSFORM_NONE;
     // Format of the buffer to composite.
-    SurfaceFactoryOzone::BufferFormat format = SurfaceFactoryOzone::UNKNOWN;
+    NativePixmapFormat format = NATIVE_PIXMAP_FORMAT_BGRA_8888;
     // Size of the buffer, in pixels.
     gfx::Size buffer_size;
     // Rect on the display to position the overlay to. Input rectangle may