--- a/embedding/components/printingui/ipc/PPrintingTypes.ipdlh
+++ b/embedding/components/printingui/ipc/PPrintingTypes.ipdlh
@@ -113,12 +113,14 @@ struct PrintData {
    */
   float scalingFactor;
   /*
    * Scaling factor for converting from OS X native paper size
    * units to inches.
    */
   float widthScale;
   float heightScale;
+  double adjustedPaperWidth;
+  double adjustedPaperHeight;
 };
 
 } // namespace embedding
 } // namespace mozilla

--- a/widget/cocoa/nsPrintDialogX.mm
+++ b/widget/cocoa/nsPrintDialogX.mm
@@ -140,17 +140,28 @@ nsPrintDialogServiceX::Show(nsPIDOMWindo
   bool isShrinkToFitChecked;
   settingsX->GetShrinkToFit(&isShrinkToFitChecked);
   if (isShrinkToFitChecked) {
     NSMutableDictionary* dict = [copy dictionary];
     if (dict) {
       [dict setObject: [NSNumber numberWithFloat: 1]
                forKey: NSPrintScalingFactor];
     }
+    // Set the scaling factor to 100% in the NSPrintInfo
+    // object so that it will not affect the paper size
+    // retrieved from the PMPageFormat routines.
+    [copy setScalingFactor:1.0];
+  } else {
+    aSettings->SetScaling([copy scalingFactor]);
   }
+
+  // Set the adjusted paper size now that we've updated
+  // the scaling factor.
+  settingsX->InitAdjustedPaperSize();
+
   [copy release];
 
   int16_t pageRange;
   aSettings->GetPrintRange(&pageRange);
   if (pageRange != nsIPrintSettings::kRangeSelection) {
     PMPrintSettings nativePrintSettings = settingsX->GetPMPrintSettings();
     UInt32 firstPage, lastPage;
     OSStatus status = ::PMGetFirstPage(nativePrintSettings, &firstPage);

--- a/widget/cocoa/nsPrintOptionsX.mm
+++ b/widget/cocoa/nsPrintOptionsX.mm
@@ -66,16 +66,21 @@ nsPrintOptionsX::SerializeToPrintData(ns
     return NS_ERROR_FAILURE;
   }
 
   NSPrintInfo* printInfo = settingsX->GetCocoaPrintInfo();
   if (NS_WARN_IF(!printInfo)) {
     return NS_ERROR_FAILURE;
   }
 
+  double adjustedWidth, adjustedHeight;
+  settingsX->GetAdjustedPaperSize(&adjustedWidth, &adjustedHeight);
+  data->adjustedPaperWidth() = adjustedWidth;
+  data->adjustedPaperHeight() = adjustedHeight;
+
   NSDictionary* dict = [printInfo dictionary];
   if (NS_WARN_IF(!dict)) {
     return NS_ERROR_FAILURE;
   }
 
   NSString* printerName = [dict objectForKey: NSPrintPrinterName];
   if (printerName) {
     nsCocoaUtils::GetStringForNSString(printerName, data->printerName());
@@ -280,16 +285,19 @@ nsPrintOptionsX::DeserializeToPrintSetti
   if (NS_WARN_IF(!newPrintInfo)) {
     return NS_ERROR_OUT_OF_MEMORY;
   }
 
   // And now swap in the new NSPrintInfo we've just populated.
   settingsX->SetCocoaPrintInfo(newPrintInfo);
   [newPrintInfo release];
 
+  settingsX->SetAdjustedPaperSize(data.adjustedPaperWidth(),
+                                  data.adjustedPaperHeight());
+
   return NS_OK;
 }
 
 nsresult
 nsPrintOptionsX::ReadPrefs(nsIPrintSettings* aPS, const nsAString& aPrinterName, uint32_t aFlags)
 {
   nsresult rv;
   

--- a/widget/cocoa/nsPrintSettingsX.h
+++ b/widget/cocoa/nsPrintSettingsX.h
@@ -20,29 +20,45 @@ public:
   NS_DECL_ISUPPORTS_INHERITED
 
   nsPrintSettingsX();
   nsresult Init();
   NSPrintInfo* GetCocoaPrintInfo() { return mPrintInfo; }
   void SetCocoaPrintInfo(NSPrintInfo* aPrintInfo);
   virtual nsresult ReadPageFormatFromPrefs();
   virtual nsresult WritePageFormatToPrefs();
+  virtual nsresult GetEffectivePageSize(double *aWidth,
+      double *aHeight) override;
+
+  // In addition to setting the paper width and height, these
+  // overrides set the adjusted width and height returned from
+  // GetEffectivePageSize. This is needed when a paper size is
+  // set manually without using a print dialog a la reftest-print.
+  virtual nsresult SetPaperWidth(double aPaperWidth) override;
+  virtual nsresult SetPaperHeight(double aPaperWidth) override;
 
   PMPrintSettings GetPMPrintSettings();
   PMPrintSession GetPMPrintSession();
   PMPageFormat GetPMPageFormat();
   void SetPMPageFormat(PMPageFormat aPageFormat);
 
   // Re-initialize mUnwriteableMargin with values from mPageFormat.
   // Should be called whenever mPageFormat is initialized or overwritten.
   nsresult InitUnwriteableMargin();
 
+  // Re-initialize mAdjustedPaper{Width,Height} with values from mPageFormat.
+  // Should be called whenever mPageFormat is initialized or overwritten.
+  nsresult InitAdjustedPaperSize();
+
   void SetInchesScale(float aWidthScale, float aHeightScale);
   void GetInchesScale(float *aWidthScale, float *aHeightScale);
 
+  void SetAdjustedPaperSize(double aWidth, double aHeight);
+  void GetAdjustedPaperSize(double *aWidth, double *aHeight);
+
 protected:
   virtual ~nsPrintSettingsX();
 
   nsPrintSettingsX(const nsPrintSettingsX& src);
   nsPrintSettingsX& operator=(const nsPrintSettingsX& rhs);
 
   nsresult _Clone(nsIPrintSettings **_retval) override;
   nsresult _Assign(nsIPrintSettings *aPS) override;
@@ -52,13 +68,15 @@ protected:
   OSStatus CreateDefaultPrintSettings(PMPrintSession aSession, PMPrintSettings& outSettings);
 
   NSPrintInfo* mPrintInfo;
 
   // Scaling factors used to convert the NSPrintInfo
   // paper size units to inches
   float mWidthScale;
   float mHeightScale;
+  double mAdjustedPaperWidth;
+  double mAdjustedPaperHeight;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsPrintSettingsX, NS_PRINTSETTINGSX_IID)
 
 #endif // nsPrintSettingsX_h_

--- a/widget/cocoa/nsPrintSettingsX.mm
+++ b/widget/cocoa/nsPrintSettingsX.mm
@@ -63,16 +63,17 @@ nsPrintSettingsX& nsPrintSettingsX::oper
   NS_OBJC_END_TRY_ABORT_BLOCK_RETURN(*this);
 }
 
 nsresult nsPrintSettingsX::Init()
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
 
   InitUnwriteableMargin();
+  InitAdjustedPaperSize();
 
   return NS_OK;
 
   NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
 }
 
 // Should be called whenever the page format changes.
 NS_IMETHODIMP nsPrintSettingsX::InitUnwriteableMargin()
@@ -89,16 +90,33 @@ NS_IMETHODIMP nsPrintSettingsX::InitUnwr
   mUnwriteableMargin.bottom = NS_POINTS_TO_INT_TWIPS(paperMargin.bottom);
   mUnwriteableMargin.right  = NS_POINTS_TO_INT_TWIPS(paperMargin.right);
 
   return NS_OK;
 
   NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;  
 }
 
+NS_IMETHODIMP nsPrintSettingsX::InitAdjustedPaperSize()
+{
+  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
+
+  PMPageFormat pageFormat = GetPMPageFormat();
+
+  PMRect paperRect;
+  ::PMGetAdjustedPaperRect(pageFormat, &paperRect);
+
+  mAdjustedPaperWidth = paperRect.right - paperRect.left;
+  mAdjustedPaperHeight = paperRect.bottom - paperRect.top;
+
+  return NS_OK;
+
+  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
+}
+
 void
 nsPrintSettingsX::SetCocoaPrintInfo(NSPrintInfo* aPrintInfo)
 {
   if (mPrintInfo != aPrintInfo) {
     [mPrintInfo release];
     mPrintInfo = [aPrintInfo retain];
   }
 }
@@ -201,18 +219,54 @@ nsPrintSettingsX::SetPMPageFormat(PMPage
   PMPageFormat oldPageFormat = GetPMPageFormat();
   ::PMCopyPageFormat(aPageFormat, oldPageFormat);
   [mPrintInfo updateFromPMPageFormat];
 }
 
 void
 nsPrintSettingsX::SetInchesScale(float aWidthScale, float aHeightScale)
 {
-  mWidthScale = aWidthScale;
-  mHeightScale = aHeightScale;
+  if (aWidthScale > 0 && aHeightScale > 0) {
+    mWidthScale = aWidthScale;
+    mHeightScale = aHeightScale;
+  }
 }
 
 void
 nsPrintSettingsX::GetInchesScale(float *aWidthScale, float *aHeightScale)
 {
   *aWidthScale = mWidthScale;
   *aHeightScale = mHeightScale;
 }
+
+NS_IMETHODIMP nsPrintSettingsX::SetPaperWidth(double aPaperWidth)
+{
+  mPaperWidth = aPaperWidth;
+  mAdjustedPaperWidth = aPaperWidth * mWidthScale;
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsPrintSettingsX::SetPaperHeight(double aPaperHeight)
+{
+  mPaperHeight = aPaperHeight;
+  mAdjustedPaperHeight = aPaperHeight * mHeightScale;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrintSettingsX::GetEffectivePageSize(double *aWidth, double *aHeight)
+{
+  *aWidth  = NS_INCHES_TO_TWIPS(mAdjustedPaperWidth / mWidthScale);
+  *aHeight = NS_INCHES_TO_TWIPS(mAdjustedPaperHeight / mHeightScale);
+  return NS_OK;
+}
+
+void nsPrintSettingsX::SetAdjustedPaperSize(double aWidth, double aHeight)
+{
+  mAdjustedPaperWidth = aWidth;
+  mAdjustedPaperHeight = aHeight;
+}
+
+void nsPrintSettingsX::GetAdjustedPaperSize(double *aWidth, double *aHeight)
+{
+  *aWidth = mAdjustedPaperWidth;
+  *aHeight = mAdjustedPaperHeight;
+}