gfx: Make conversions from gfx::Point to PointF explicit.

cc/trees/occlusion_tracker_perftest.cc

Index: cc/trees/occlusion_tracker_perftest.cc
diff --git a/cc/trees/occlusion_tracker_perftest.cc b/cc/trees/occlusion_tracker_perftest.cc
index 01b63de6279a7a092908b496c37d10d1459347ad..6113f951a58a20f2248dcb192bfe178c40ccd828 100644
--- a/cc/trees/occlusion_tracker_perftest.cc
+++ b/cc/trees/occlusion_tracker_perftest.cc
@@ -159,7 +159,7 @@ TEST_F(OcclusionTrackerPerfTest, UnoccludedContentRect_10OpaqueLayers) {
     opaque_layer->SetDrawsContent(true);
     opaque_layer->SetBounds(
         gfx::Size(viewport_rect.width() / 2, viewport_rect.height() / 2));
-    opaque_layer->SetPosition(gfx::Point(i, i));
+    opaque_layer->SetPosition(gfx::PointF(i, i));
     active_tree()->root_layer()->AddChild(opaque_layer.Pass());
   }