Bug 1399787 - Part 14. Prevent RemotePrintJobChild using ipc calls after the channel was destroyed. r=jwatt

If in the future nsDeviceContextSpecWin::BeginDocument was to return
NS_ERROR_FAILURE, then the channel between RemotePrintJobParent and
RemotePrintJobChild will be close at [1]. RemotePrintJobChild keep using ipc
calls after the channel is broken and hits assertions.

PS:
We always hits this assertion by forcing nsDeviceContextSpecWin::BeginDocument
returning NS_ERROR_FAILURE. It's not relative to the change we made in
previous patches.

[1]
https://hg.mozilla.org/mozilla-central/file/b186fddce27f/layout/printing/ipc/RemotePrintJobParent.cpp#l44
MozReview-Commit-ID: 79mZBf301nb

--HG--
extra : rebase_source : 58076a18be56d7eea37ea2f5a147db0048e3493f
extra : intermediate-source : 88df2caad42694dd77f2a518ea8d460d6c88b8c6
extra : source : b920088860904c5d28f3dd2f6eda790dc09be003

layout/printing/ipc/RemotePrintJobChild.cpp

@@ -71,7 +71,9 @@ RemotePrintJobChild::ProcessPage()
   MOZ_ASSERT(mPagePrintTimer);
 
   mPagePrintTimer->WaitForRemotePrint();
-  Unused << SendProcessPage();
+  if (!mDestroyed) {
+    Unused << SendProcessPage();
+  }
 }
 
 mozilla::ipc::IPCResult
@@ -116,7 +118,10 @@ RemotePrintJobChild::OnStateChange(nsIWebProgress* aProgress,
                                    nsIRequest* aRequest, uint32_t aStateFlags,
                                    nsresult aStatus)
 {
-  Unused << SendStateChange(aStateFlags, aStatus);
+  if (!mDestroyed) {
+    Unused << SendStateChange(aStateFlags, aStatus);
+  }
+
   return NS_OK;
 }
 
@@ -128,8 +133,11 @@ RemotePrintJobChild::OnProgressChange(nsIWebProgress * aProgress,
                                       int32_t aCurTotalProgress,
                                       int32_t aMaxTotalProgress)
 {
-  Unused << SendProgressChange(aCurSelfProgress, aMaxSelfProgress,
-                               aCurTotalProgress, aMaxTotalProgress);
+  if (!mDestroyed) {
+    Unused << SendProgressChange(aCurSelfProgress, aMaxSelfProgress,
+                                 aCurTotalProgress, aMaxTotalProgress);
+  }
+
   return NS_OK;
 }
 
@@ -146,7 +154,10 @@ RemotePrintJobChild::OnStatusChange(nsIWebProgress* aProgress,
                                     nsIRequest* aRequest, nsresult aStatus,
                                     const char16_t* aMessage)
 {
-  Unused << SendStatusChange(aStatus);
+  if (!mDestroyed) {
+    Unused << SendStatusChange(aStatus);
+  }
+
   return NS_OK;
 }
 
@@ -168,6 +179,8 @@ RemotePrintJobChild::ActorDestroy(ActorDestroyReason aWhy)
 {
   mPagePrintTimer = nullptr;
   mPrintEngine = nullptr;
+
+  mDestroyed = true;
 }
 
 } // namespace layout

layout/printing/ipc/RemotePrintJobChild.h

@@ -55,6 +55,7 @@ private:
   void SetNextPageFD(const mozilla::ipc::FileDescriptor& aFd);
 
   bool mPrintInitialized = false;
+  bool mDestroyed = false;
   nsresult mInitializationResult = NS_OK;
   RefPtr<nsPagePrintTimer> mPagePrintTimer;
   RefPtr<nsPrintEngine> mPrintEngine;