Bug 1420743 P1 Do a better job of clearing docshell's mInitialClientSource at the end of page load. r=baku

docshell/base/nsDocShell.cpp

@@ -7801,6 +7801,11 @@ nsDocShell::EndPageLoad(nsIWebProgress* aProgress,
     return NS_ERROR_NULL_POINTER;
   }
 
+  // Make sure to discard the initial client if we never created the initial
+  // about:blank document.  Do this before possibly returning from the method
+  // due to an error.
+  mInitialClientSource.reset();
+
   nsCOMPtr<nsIConsoleReportCollector> reporter = do_QueryInterface(aChannel);
   if (reporter) {
     nsCOMPtr<nsILoadGroup> loadGroup;
@@ -7836,10 +7841,6 @@ nsDocShell::EndPageLoad(nsIWebProgress* aProgress,
   // Timing is picked up by the window, we don't need it anymore
   mTiming = nullptr;
 
-  // Make sure to discard the initial client if we never created the initial
-  // about:blank document.
-  mInitialClientSource.reset();
-
   // clean up reload state for meta charset
   if (eCharsetReloadRequested == mCharsetReloadState) {
     mCharsetReloadState = eCharsetReloadStopOrigional;
@@ -11835,6 +11836,11 @@ nsDocShell::DoChannelLoad(nsIChannel* aChannel,
     openFlags |= nsIURILoader::DONT_RETARGET;
   }
 
+  // If anything fails here, make sure to clear our initial ClientSource.
+  auto cleanupInitialClient = MakeScopeExit([&] {
+    mInitialClientSource.reset();
+  });
+
   nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
   NS_ENSURE_TRUE(win, NS_ERROR_FAILURE);
 
@@ -11860,6 +11866,9 @@ nsDocShell::DoChannelLoad(nsIChannel* aChannel,
   // collector slice
   nsJSContext::MaybeRunNextCollectorSlice(this, JS::gcreason::DOCSHELL);
 
+  // Success.  Keep the initial ClientSource if it exists.
+  cleanupInitialClient.release();
+
   return NS_OK;
 }
 

dom/base/nsGlobalWindowInner.cpp

@@ -1749,6 +1749,14 @@ nsGlobalWindowInner::EnsureClientSource()
   nsCOMPtr<nsIChannel> channel = mDoc->GetChannel();
   nsCOMPtr<nsILoadInfo> loadInfo = channel ? channel->GetLoadInfo() : nullptr;
 
+  // Take the initial client source from the docshell immediately.  Even if we
+  // don't end up using it here we should consume it.
+  UniquePtr<ClientSource> initialClientSource;
+  nsIDocShell* docshell = GetDocShell();
+  if (docshell) {
+    initialClientSource = docshell->TakeInitialClientSource();
+  }
+
   // Try to get the reserved client from the LoadInfo.  A Client is
   // reserved at the start of the channel load if there is not an
   // initial about:blank document that will be reused.  It is also
@@ -1769,12 +1777,9 @@ nsGlobalWindowInner::EnsureClientSource()
   // and it created an initial Client as a placeholder for the document.
   // In this case we want to inherit this placeholder Client here.
   if (!mClientSource) {
-    nsIDocShell* docshell = GetDocShell();
-    if (docshell) {
-      mClientSource = docshell->TakeInitialClientSource();
-      if (mClientSource) {
-        newClientSource = true;
-      }
+    mClientSource = Move(initialClientSource);
+    if (mClientSource) {
+      newClientSource = true;
     }
   }