Revert of Change call-sites now that SkCanvas is not ref-counted

content/renderer/pepper/pepper_plugin_instance_impl.h

Index: content/renderer/pepper/pepper_plugin_instance_impl.h
diff --git a/content/renderer/pepper/pepper_plugin_instance_impl.h b/content/renderer/pepper/pepper_plugin_instance_impl.h
index 37da8a1477c7ca8bed6073effa39fb7e13bf28c5..cac1a756e4ee03bf98efa6cf5c860e1713df6490 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.h
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.h
@@ -836,9 +836,8 @@
   // is preserved in PrintWebViewHelper::PrintPages. This makes it possible
   // to generate the entire PDF given the variables below:
   //
-  // The most recently used WebCanvas to be used in printEnd(). Caller must
-  // ensure that it remains valid until that point.
-  blink::WebCanvas* canvas_;
+  // The most recently used WebCanvas, guaranteed to be valid.
+  sk_sp<blink::WebCanvas> canvas_;
   // An array of page ranges.
   std::vector<PP_PrintPageNumberRange_Dev> ranges_;