Bug 799078. Part 1: Expose nsContentUtils::FindPresShellForDocument. r=matspal

--HG--
extra : rebase_source : f7e6410637ea70fe2d68fdcc24bcb409816d5bd7

content/base/public/nsContentUtils.h

@@ -1822,12 +1822,23 @@ public:
                                          const nsAString& aClasses,
                                          nsIDOMNodeList** aReturn);
 
+  /**
+   * Returns a presshell for this document, if there is one. This will be
+   * aDoc's direct presshell if there is one, otherwise we'll look at all
+   * ancestor documents to try to find a presshell, so for example this can
+   * still find a presshell for documents in display:none frames that have
+   * no presentation. So you have to be careful how you use this presshell ---
+   * getting generic data like a device context or widget from it is OK, but it
+   * might not be this document's actual presentation.
+   */
+  static nsIPresShell* FindPresShellForDocument(nsIDocument* aDoc);
+
   /**
    * Returns the widget for this document if there is one. Looks at all ancestor
    * documents to try to find a widget, so for example this can still find a
    * widget for documents in display:none frames that have no presentation.
    */
-  static nsIWidget *WidgetForDocument(nsIDocument *aDoc);
+  static nsIWidget* WidgetForDocument(nsIDocument* aDoc);
 
   /**
    * Returns a layer manager to use for the given document. Basically we

content/base/src/nsContentUtils.cpp

@@ -6524,8 +6524,8 @@ nsContentUtils::PlatformToDOMLineBreaks(nsString &aString)
   }
 }
 
-nsIWidget *
-nsContentUtils::WidgetForDocument(nsIDocument *aDoc)
+nsIPresShell*
+nsContentUtils::FindPresShellForDocument(nsIDocument* aDoc)
 {
   nsIDocument* doc = aDoc;
   nsIDocument* displayDoc = doc->GetDisplayDocument();
@@ -6534,25 +6534,35 @@ nsContentUtils::WidgetForDocument(nsIDocument *aDoc)
   }
 
   nsIPresShell* shell = doc->GetShell();
+  if (shell) {
+    return shell;
+  }
+
   nsCOMPtr<nsISupports> container = doc->GetContainer();
   nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = do_QueryInterface(container);
-  while (!shell && docShellTreeItem) {
+  while (docShellTreeItem) {
     // We may be in a display:none subdocument, or we may not have a presshell
     // created yet.
     // Walk the docshell tree to find the nearest container that has a presshell,
-    // and find the root widget from that.
+    // and return that.
     nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(docShellTreeItem);
     nsCOMPtr<nsIPresShell> presShell;
     docShell->GetPresShell(getter_AddRefs(presShell));
     if (presShell) {
-      shell = presShell;
-    } else {
-      nsCOMPtr<nsIDocShellTreeItem> parent;
-      docShellTreeItem->GetParent(getter_AddRefs(parent));
-      docShellTreeItem = parent;
+      return presShell;
     }
+    nsCOMPtr<nsIDocShellTreeItem> parent;
+    docShellTreeItem->GetParent(getter_AddRefs(parent));
+    docShellTreeItem = parent;
   }
 
+  return nullptr;
+}
+
+nsIWidget*
+nsContentUtils::WidgetForDocument(nsIDocument* aDoc)
+{
+  nsIPresShell* shell = FindPresShellForDocument(aDoc);
   if (shell) {
     nsIViewManager* VM = shell->GetViewManager();
     if (VM) {