PlzNavigate: identify same-page browser-initiated navigation.

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 7f196f9b7a518255cecee1135a652d8b8df24299..3e363cea9b51357b9c162d090e160b9024df126e 100644
--- a/third_party/WebKit/Source/core/loader/FrameLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
@@ -1193,6 +1193,14 @@ void FrameLoader::load(const FrameLoadRequest& passedRequest,
     return;
   }
 
+  // PlzNavigate
+  // If the loader classifies this navigation as a different document navigation
+  // while the browser intended the navigation to be same-document, it means
+  // that a different navigation must have committed while the IPC was sent.
+  // This navigation is no more same-document. The navigation is simply dropped.
+  if (request.resourceRequest().isSameDocumentNavigation())
+    return;
+
   startLoad(request, newLoadType, policy);
 }