Bug 1516180 - Provide principal when saving content. r=IanN

Port Bug 1469916.

suite/base/content/nsContextMenu.js

@@ -967,7 +967,8 @@ nsContextMenu.prototype = {
     saveImageURL(canvas.toDataURL("image/jpeg", ""), name, "SaveImageTitle",
                                   true, true,
                                   this.target.ownerDocument.documentURIObject,
-                                  null, null, null, (gPrivate ? true : false));
+                                  null, null, null, (gPrivate ? true : false),
+                                  this.target.ownerDocument.nodePrincipal);
   },
 
   // Full screen video playback
@@ -1143,12 +1144,14 @@ nsContextMenu.prototype = {
       // Bypass cache, since it's a data: URL.
       saveImageURL(this.target.toDataURL(), "canvas.png", "SaveImageTitle",
                    true, false, referrerURI, null, null, null,
-                   (gPrivate ? true : false));
+                   (gPrivate ? true : false),
+                   doc.nodePrincipal /* system, because blob: */);
     else if (this.onImage) {
       saveImageURL(this.mediaURL, null, "SaveImageTitle", false,
                    false, referrerURI, null, gContextMenuContentData.contentType,
                    gContextMenuContentData.contentDisposition,
-                   (gPrivate ? true : false));
+                   (gPrivate ? true : false),
+                   doc.nodePrincipal);
     }
     else if (this.onVideo || this.onAudio) {
       var dialogTitle = this.onVideo ? "SaveVideoTitle" : "SaveAudioTitle";

suite/browser/pageinfo/pageInfo.js

@@ -916,7 +916,8 @@ function saveMedia()
         titleKey = "SaveAudioTitle";
 
       saveURL(url, null, titleKey, false, false, makeURI(item.baseURI),
-              null, (opener.gPrivate ? true : false));
+              null, (opener.gPrivate ? true : false),
+              gDocument.nodePrincipal);
     }
   } else {
     selectSaveFolder(function(aDirectory) {
@@ -925,7 +926,8 @@ function saveMedia()
           uniqueFile(aChosenData.file);
           internalSave(aURIString, null, null, null, null, false,
                        "SaveImageTitle", aChosenData, aBaseURI, null, false,
-                       null, (opener.gPrivate ? true : false));
+                       null, (opener.gPrivate ? true : false),
+                       gDocument.nodePrincipal);
         };
 
         for (var i = 0; i < rowArray.length; i++) {

suite/components/shell/nsMacShellService.cpp

@@ -173,7 +173,7 @@ nsMacShellService::SetDesktopBackground(Element* aElement,
     loadContext = do_QueryInterface(docShell);
   }
 
-  return wbp->SaveURI(imageURI, 0,
+  return wbp->SaveURI(imageURI, aElement->NodePrincipal(), 0,
                       docURI, aElement->OwnerDoc()->GetReferrerPolicy(),
                       nullptr, nullptr,
                       mBackgroundFile, loadContext);