Always use FrameNavigationDisabler during DocumentLoader detach.

third_party/WebKit/Source/core/loader/FrameLoader.cpp

Index: third_party/WebKit/Source/core/loader/FrameLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/FrameLoader.cpp b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
index 440f0a8f70bf33bfead5ab871e8c979e8386c600..a55f4d0157fcfccb37b42772c2211d76570f1b68 100644
--- a/third_party/WebKit/Source/core/loader/FrameLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
@@ -724,6 +724,7 @@ void FrameLoader::detachDocumentLoader(Member<DocumentLoader>& loader)
     if (!loader)
         return;
 
+    FrameNavigationDisabler navigationDisabler(*m_frame);
     loader->detachFromFrame();
     loader = nullptr;
 }
@@ -1108,7 +1109,6 @@ bool FrameLoader::prepareForCommit()
     // At this point, the provisional document loader should not detach, because
     // then the FrameLoader would not have any attached DocumentLoaders.
     if (m_documentLoader) {
-        FrameNavigationDisabler navigationDisabler(*m_frame);
         TemporaryChange<bool> inDetachDocumentLoader(m_protectProvisionalLoader, true);
         detachDocumentLoader(m_documentLoader);
     }
@@ -1419,10 +1419,7 @@ void FrameLoader::startLoad(FrameLoadRequest& frameLoadRequest, FrameLoadType ty
         return;
 
     m_frame->document()->cancelParsing();
-    if (m_provisionalDocumentLoader) {
-        FrameNavigationDisabler navigationDisabler(*m_frame);
-        detachDocumentLoader(m_provisionalDocumentLoader);
-    }
+    detachDocumentLoader(m_provisionalDocumentLoader);
 
     // beforeunload fired above, and detaching a DocumentLoader can fire
     // events, which can detach this frame.