Allow navigations to frames that aren't being unloaded in the unload handler.

third_party/WebKit/Source/core/frame/History.cpp

Index: third_party/WebKit/Source/core/frame/History.cpp
diff --git a/third_party/WebKit/Source/core/frame/History.cpp b/third_party/WebKit/Source/core/frame/History.cpp
index d6f76e68d4dfdabdded50b82bdfa00d8c79585fa..6e951be2952fecce123c92b3cdda74b313f592b8 100644
--- a/third_party/WebKit/Source/core/frame/History.cpp
+++ b/third_party/WebKit/Source/core/frame/History.cpp
@@ -139,11 +139,11 @@ void History::go(ExecutionContext* context, int delta) {
     return;
 
   if (!activeDocument->frame() ||
-      !activeDocument->frame()->canNavigate(*frame())) {
+      !activeDocument->frame()->canNavigate(*frame()) ||
+      !activeDocument->frame()->isNavigationAllowed() ||
+      !NavigationDisablerForBeforeUnload::isNavigationAllowed()) {
     return;
   }
-  if (!NavigationDisablerForUnload::isNavigationAllowed())
-    return;
 
   if (delta) {
     frame()->loader().client()->navigateBackForward(delta);