Change the scale factor of texture_size from the layer's one to an estimation.

ui/compositor/layer.h

Index: ui/compositor/layer.h
diff --git a/ui/compositor/layer.h b/ui/compositor/layer.h
index 5ce3fed4d5b8fe0c43e15be77949a2de0efbc187..055fdf72ea8d495dfc028ffe0e2c359e90bc0df2 100644
--- a/ui/compositor/layer.h
+++ b/ui/compositor/layer.h
@@ -394,6 +394,11 @@ class COMPOSITOR_EXPORT Layer
   // A cached copy of |Compositor::device_scale_factor()|.
   float device_scale_factor_;
 
+  // The device scale factor when |texture_| is provided.  This is mostly same
+  // as |device_scale_factor_| itself but could be inconsistent in some special
+  // cases.
+  float device_scale_factor_for_texture_;
+
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };