Bug 1705757 - Move FrameLoader.print to BrowsingContext.print. r=nika,remote-protocol-reviewers,marionette-reviewers,extension-reviewers,zombie

This makes it trivial to choose the right BrowserParent to print a
browsing context, by removing the OuterWindowID / FrameLoader
indirections.

Differential Revision: https://phabricator.services.mozilla.com/D112412

toolkit/content/widgets/browser-custom-element.js

@@ -1731,14 +1731,6 @@
       };
     }
 
-    print(aOuterWindowID, aPrintSettings) {
-      if (!this.frameLoader) {
-        throw Components.Exception("No frame loader.", Cr.NS_ERROR_FAILURE);
-      }
-
-      return this.frameLoader.print(aOuterWindowID, aPrintSettings);
-    }
-
     async drawSnapshot(x, y, w, h, scale, backgroundColor) {
       let rect = new DOMRect(x, y, w, h);
       try {