Bug 1245978 part 2: Drop redundant 'virtual' keyword from NS_DECL_NSIDOCUMENTVIEWERPRINT macro (which already includes 'override' keyword). r=heycam

This makes these lines shorter, and brings us into alignment with the Mozilla Coding Style Guide. See mozilla.dev.platform post "Proposal to alter the coding style to not require the usage of 'virtual' where 'override' is used" for more info.

layout/base/nsIDocumentViewerPrint.h

@@ -69,17 +69,17 @@ NS_DEFINE_STATIC_IID_ACCESSOR(nsIDocumentViewerPrint,
 
 /* Use this macro when declaring classes that implement this interface. */
 #define NS_DECL_NSIDOCUMENTVIEWERPRINT \
-  virtual void     SetIsPrinting(bool aIsPrinting) override; \
-  virtual bool     GetIsPrinting() override; \
-  virtual void     SetIsPrintPreview(bool aIsPrintPreview) override; \
-  virtual bool     GetIsPrintPreview() override; \
-  virtual mozilla::StyleSetHandle CreateStyleSet(nsIDocument* aDocument) override; \
-  virtual void     IncrementDestroyRefCount() override; \
-  virtual void     ReturnToGalleyPresentation() override; \
-  virtual void     OnDonePrinting() override; \
-  virtual bool     IsInitializedForPrintPreview() override; \
-  virtual void     InitializeForPrintPreview() override; \
-  virtual void     SetPrintPreviewPresentation(nsViewManager* aViewManager, \
+  void     SetIsPrinting(bool aIsPrinting) override; \
+  bool     GetIsPrinting() override; \
+  void     SetIsPrintPreview(bool aIsPrintPreview) override; \
+  bool     GetIsPrintPreview() override; \
+  mozilla::StyleSetHandle CreateStyleSet(nsIDocument* aDocument) override; \
+  void     IncrementDestroyRefCount() override; \
+  void     ReturnToGalleyPresentation() override; \
+  void     OnDonePrinting() override; \
+  bool     IsInitializedForPrintPreview() override; \
+  void     InitializeForPrintPreview() override; \
+  void     SetPrintPreviewPresentation(nsViewManager* aViewManager, \
                                        nsPresContext* aPresContext, \
                                        nsIPresShell* aPresShell) override;