check for null-device before using the windowless canvas

content/plugin/webplugin_proxy.cc

Index: content/plugin/webplugin_proxy.cc
===================================================================
--- content/plugin/webplugin_proxy.cc	(revision 123470)
+++ content/plugin/webplugin_proxy.cc	(working copy)
@@ -339,7 +339,7 @@
   if (!windowless_context())
     return;
 #else
-  if (!windowless_canvas())
+  if (!windowless_canvas() || !windowless_canvas()->getDevice())
     return;
 #endif
 
@@ -390,7 +390,7 @@
   windowless_canvas()->clipRect(sk_rect);
 
   // Setup the background.
-  if (background_canvas_.get()) {
+  if (background_canvas_.get() && background_canvas_.get()->getDevice()) {
     // When a background canvas is given, we're in transparent mode. This means
     // the plugin wants to have the image of the page in the canvas it's drawing
     // into (which is windowless_canvases_) so it can do blending. So we copy