diff --git a/content/base/public/nsIDocument.h b/content/base/public/nsIDocument.h
index c6dbe5e334e4..175085afbd11 100644
--- a/content/base/public/nsIDocument.h
+++ b/content/base/public/nsIDocument.h
@@ -705,6 +705,14 @@ public:
    */
   virtual void FlushPendingNotifications(mozFlushType aType) = 0;
 
+  /**
+   * Calls FlushPendingNotifications on any external resources this document
+   * has. If this document has no external resources or is an external resource
+   * itself this does nothing. This should only be called with
+   * aType >= Flush_Style.
+   */
+  virtual void FlushExternalResources(mozFlushType aType) = 0;
+
   nsBindingManager* BindingManager() const
   {
     return mNodeInfoManager->GetBindingManager();
diff --git a/content/base/src/nsDocument.cpp b/content/base/src/nsDocument.cpp
index 8da2c8ea9e9c..a562f879e809 100644
--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -6445,6 +6445,26 @@ nsDocument::FlushPendingNotifications(mozFlushType aType)
   }
 }
 
+static PRBool
+Flush(nsIDocument* aDocument, void* aData)
+{
+  const mozFlushType* type = static_cast<const mozFlushType*>(aData);
+  aDocument->FlushPendingNotifications(*type);
+  return PR_TRUE;
+}
+
+void
+nsDocument::FlushExternalResources(mozFlushType aType)
+{
+  NS_ASSERTION(aType >= Flush_Style,
+    "should only need to flush for style or higher in external resources");
+
+  if (GetDisplayDocument()) {
+    return;
+  }
+  EnumerateExternalResources(Flush, &aType);
+}
+
 nsIScriptEventManager*
 nsDocument::GetScriptEventManager()
 {
diff --git a/content/base/src/nsDocument.h b/content/base/src/nsDocument.h
index 834794e859cf..687cad6ffffd 100644
--- a/content/base/src/nsDocument.h
+++ b/content/base/src/nsDocument.h
@@ -704,6 +704,7 @@ public:
                                 nsIStyleRule* aStyleRule);
 
   virtual void FlushPendingNotifications(mozFlushType aType);
+  virtual void FlushExternalResources(mozFlushType aType);
   virtual nsIScriptEventManager* GetScriptEventManager();
   virtual void SetXMLDeclaration(const PRUnichar *aVersion,
                                  const PRUnichar *aEncoding,
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 2453b73cb1bb..9dde8f0e4fe7 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -4589,6 +4589,14 @@ PresShell::FlushPendingNotifications(mozFlushType aType)
     // batching if we only have style reresolve
     nsIViewManager::UpdateViewBatch batch(mViewManager);
 
+    // We need to make sure external resource documents are flushed too (for
+    // example, svg filters that reference a filter in an external document
+    // need the frames in the external document to be constructed for the
+    // filter to work). We only need external resources to be flushed when the
+    // main document is flushing >= Flush_Frames, so we flush external
+    // resources here instead of nsDocument::FlushPendingNotifications.
+    mDocument->FlushExternalResources(aType);
+
     // Force flushing of any pending content notifications that might have
     // queued up while our event was pending.  That will ensure that we don't
     // construct frames for content right now that's still waiting to be