Make SkOSWindow windows implementation use CS_OWNDC in its window class

TBR=joshualitt@google.com

Review URL: https://codereview.chromium.org/1413213005
diff --git a/src/views/win/skia_win.cpp b/src/views/win/skia_win.cpp
index 6f1db77..c15846d 100644
--- a/src/views/win/skia_win.cpp
+++ b/src/views/win/skia_win.cpp
@@ -22,7 +22,7 @@
 
     wcex.cbSize = sizeof(WNDCLASSEX);
 
-    wcex.style          = CS_HREDRAW | CS_VREDRAW;
+    wcex.style          = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
     wcex.lpfnWndProc    = WndProc;
     wcex.cbClsExtra     = 0;
     wcex.cbWndExtra     = 0;