Revert "Bug 1996506 - Don't climb above document in GetNonGenericParent. r=Jamie" for causing mass failures.

This reverts commit ec0aa56.

Author: agoloman

accessible/basetypes/Accessible.h

@@ -705,12 +705,11 @@ class Accessible {
   }
 
   /**
-   * Returns the nearest ancestor in the document which is not a generic
-   * element.
+   * Returns the nearest ancestor which is not a generic element.
    */
   Accessible* GetNonGenericParent() const {
     for (Accessible* parent = Parent(); parent; parent = parent->Parent()) {
-      if (parent->IsDoc() || !parent->IsGeneric()) {
+      if (!parent->IsGeneric()) {
         return parent;
       }
     }

accessible/ipc/DocAccessibleParent.h

@@ -233,12 +233,7 @@ class DocAccessibleParent : public RemoteAccessible,
   // Accessible
   virtual Accessible* Parent() const override {
     if (IsTopLevel()) {
-      if (NS_IsMainThread()) {
-        return OuterDocOfRemoteBrowser();
-      } else {
-        MOZ_ASSERT_UNREACHABLE("Getting local parent off main thread!");
-        return nullptr;
-      }
+      return OuterDocOfRemoteBrowser();
     }
     return RemoteParent();
   }