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 e664eb27cae54417d51390f29bb50218095ea927..25cd699d5490e2a9c52b5b334921aef234feb68f 100644
--- a/third_party/WebKit/Source/core/loader/FrameLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameLoader.cpp
@@ -1174,7 +1174,6 @@ void FrameLoader::load(const FrameLoadRequest& passedRequest,
       shouldPerformFragmentNavigation(request.form(),
                                       request.resourceRequest().httpMethod(),
                                       newLoadType, url);
-
   // Perform same document navigation.
   if (sameDocumentHistoryNavigation || sameDocumentNavigation) {
     DCHECK(historyItem || !sameDocumentHistoryNavigation);
@@ -1193,6 +1192,14 @@ 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);
 }