Snap layers in views to physical pixel

ui/compositor/layer.h

Index: ui/compositor/layer.h
diff --git a/ui/compositor/layer.h b/ui/compositor/layer.h
index 03041edb872c1f4f66cec65a457f3ebf5aecd4ba..9ae6a4b24b30ed68fa74e07ebcb3b40f74e991b8 100644
--- a/ui/compositor/layer.h
+++ b/ui/compositor/layer.h
@@ -142,6 +142,9 @@ class COMPOSITOR_EXPORT Layer
   // The offset from our parent (stored in bounds.origin()) is an integer but we
   // may need to be at a fractional pixel offset to align properly on screen.
   void SetSubpixelPositionOffset(const gfx::Vector2dF offset);
+  const gfx::Vector2dF& subpixel_position_offset() const {
+    return subpixel_position_offset_;
+  }
 
   // Return the target bounds if animator is running, or the current bounds
   // otherwise.