Revert "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 dade2ee2e63503878d7917311a4de7a5f33ce407..dc08cfff6c7d0e8a085e2f1a3ec9db7d9faa366a 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.h
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.h
@@ -839,9 +839,8 @@ class CONTENT_EXPORT PepperPluginInstanceImpl
   // 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_;