--- a/widget/cocoa/nsCocoaWindow.h
+++ b/widget/cocoa/nsCocoaWindow.h
@@ -33,18 +33,16 @@ typedef struct _nsCocoaWindowList {
 // We don't save shadow, transparency mode or background color because it's not
 // worth the hassle - Gecko will reset them anyway as soon as the window is
 // resized.
 @interface BaseWindow : NSWindow
 {
   // Data Storage
   NSMutableDictionary* mState;
   BOOL mDrawsIntoWindowFrame;
-  NSColor* mActiveTitlebarColor;
-  NSColor* mInactiveTitlebarColor;
 
   // Invalidation disabling
   BOOL mDisabledNeedsDisplay;
 
   NSTrackingArea* mTrackingArea;
 
   NSRect mDirtyRect;
 
@@ -53,18 +51,16 @@ typedef struct _nsCocoaWindowList {
   BOOL mBrightTitlebarForeground;
   BOOL mUseMenuStyle;
 }
 
 - (void)importState:(NSDictionary*)aState;
 - (NSMutableDictionary*)exportState;
 - (void)setDrawsContentsIntoWindowFrame:(BOOL)aState;
 - (BOOL)drawsContentsIntoWindowFrame;
-- (void)setTitlebarColor:(NSColor*)aColor forActiveWindow:(BOOL)aActive;
-- (NSColor*)titlebarColorForActiveWindow:(BOOL)aActive;
 
 
 - (void)mouseEntered:(NSEvent*)aEvent;
 - (void)mouseExited:(NSEvent*)aEvent;
 - (void)mouseMoved:(NSEvent*)aEvent;
 - (void)updateTrackingArea;
 - (NSView*)trackingAreaView;
 
@@ -174,18 +170,16 @@ typedef struct _nsCocoaWindowList {
 
 // NSWindow subclass for handling windows with toolbars.
 @interface ToolbarWindow : BaseWindow
 {
   CGFloat mUnifiedToolbarHeight;
   NSRect mWindowButtonsRect;
   NSRect mFullScreenButtonRect;
 }
-// Pass nil here to get the default appearance.
-- (void)setTitlebarColor:(NSColor*)aColor forActiveWindow:(BOOL)aActive;
 - (void)setUnifiedToolbarHeight:(CGFloat)aHeight;
 - (CGFloat)unifiedToolbarHeight;
 - (CGFloat)titlebarHeight;
 - (NSRect)titlebarRect;
 - (void)setTitlebarNeedsDisplayInRect:(NSRect)aRect sync:(BOOL)aSync;
 - (void)setTitlebarNeedsDisplayInRect:(NSRect)aRect;
 - (void)setDrawsContentsIntoWindowFrame:(BOOL)aState;
 - (void)setSheetAttachmentPosition:(CGFloat)aY;
@@ -304,17 +298,16 @@ public:
     virtual void SetWindowOpacity(float aOpacity) override;
     virtual void SetWindowTransform(const mozilla::gfx::Matrix& aTransform) override;
     virtual void SetShowsToolbarButton(bool aShow) override;
     virtual void SetShowsFullScreenButton(bool aShow) override;
     virtual void SetWindowAnimationType(WindowAnimationType aType) override;
     virtual void SetDrawsTitle(bool aDrawTitle) override;
     virtual void SetUseBrightTitlebarForeground(bool aBrightForeground) override;
     virtual nsresult SetNonClientMargins(LayoutDeviceIntMargin& aMargins) override;
-    virtual void SetWindowTitlebarColor(nscolor aColor, bool aActive) override;
     virtual void SetDrawsInTitlebar(bool aState) override;
     virtual void UpdateThemeGeometries(const nsTArray<ThemeGeometry>& aThemeGeometries) override;
     virtual nsresult SynthesizeNativeMouseEvent(LayoutDeviceIntPoint aPoint,
                                                 uint32_t aNativeMessage,
                                                 uint32_t aModifierFlags,
                                                 nsIObserver* aObserver) override;
 
     void DispatchSizeModeEvent();

--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -2425,54 +2425,16 @@ nsCocoaWindow::SetNonClientMargins(Layou
 
   SetDrawsInTitlebar(margins.top == 0);
 
   return NS_OK;
 
   NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
 }
 
-void
-nsCocoaWindow::SetWindowTitlebarColor(nscolor aColor, bool aActive)
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  if (!mWindow)
-    return;
-
-  // If they pass a color with a complete transparent alpha component, use the
-  // native titlebar appearance.
-  if (NS_GET_A(aColor) == 0) {
-    [mWindow setTitlebarColor:nil forActiveWindow:(BOOL)aActive]; 
-  } else {
-    // Transform from sRGBA to monitor RGBA. This seems like it would make trying
-    // to match the system appearance lame, so probably we just shouldn't color 
-    // correct chrome.
-    if (gfxPlatform::GetCMSMode() == eCMSMode_All) {
-      qcms_transform *transform = gfxPlatform::GetCMSRGBATransform();
-      if (transform) {
-        uint8_t color[3];
-        color[0] = NS_GET_R(aColor);
-        color[1] = NS_GET_G(aColor);
-        color[2] = NS_GET_B(aColor);
-        qcms_transform_data(transform, color, color, 1);
-        aColor = NS_RGB(color[0], color[1], color[2]);
-      }
-    }
-
-    [mWindow setTitlebarColor:[NSColor colorWithDeviceRed:NS_GET_R(aColor)/255.0
-                                                    green:NS_GET_G(aColor)/255.0
-                                                     blue:NS_GET_B(aColor)/255.0
-                                                    alpha:NS_GET_A(aColor)/255.0]
-              forActiveWindow:(BOOL)aActive];
-  }
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-
 void nsCocoaWindow::SetDrawsInTitlebar(bool aState)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
   if (mWindow)
     [mWindow setDrawsContentsIntoWindowFrame:aState];
 
   NS_OBJC_END_TRY_ABORT_BLOCK;
@@ -3090,18 +3052,16 @@ static NSMutableSet *gSwizzledFrameViewC
   return frameViewClass;
 }
 
 - (id)initWithContentRect:(NSRect)aContentRect styleMask:(NSUInteger)aStyle backing:(NSBackingStoreType)aBufferingType defer:(BOOL)aFlag
 {
   mDrawsIntoWindowFrame = NO;
   [super initWithContentRect:aContentRect styleMask:aStyle backing:aBufferingType defer:aFlag];
   mState = nil;
-  mActiveTitlebarColor = nil;
-  mInactiveTitlebarColor = nil;
   mDisabledNeedsDisplay = NO;
   mTrackingArea = nil;
   mDirtyRect = NSZeroRect;
   mBeingShown = NO;
   mDrawTitle = NO;
   mBrightTitlebarForeground = NO;
   mUseMenuStyle = NO;
   [self updateTrackingArea];
@@ -3181,58 +3141,44 @@ GetMenuMaskImage()
 
 - (void)enableSetNeedsDisplay
 {
   mDisabledNeedsDisplay = NO;
 }
 
 - (void)dealloc
 {
-  [mActiveTitlebarColor release];
-  [mInactiveTitlebarColor release];
   [self removeTrackingArea];
   ChildViewMouseTracker::OnDestroyWindow(self);
   [super dealloc];
 }
 
 static const NSString* kStateTitleKey = @"title";
 static const NSString* kStateDrawsContentsIntoWindowFrameKey = @"drawsContentsIntoWindowFrame";
-static const NSString* kStateActiveTitlebarColorKey = @"activeTitlebarColor";
-static const NSString* kStateInactiveTitlebarColorKey = @"inactiveTitlebarColor";
 static const NSString* kStateShowsToolbarButton = @"showsToolbarButton";
 static const NSString* kStateCollectionBehavior = @"collectionBehavior";
 
 - (void)importState:(NSDictionary*)aState
 {
   if (NSString* title = [aState objectForKey:kStateTitleKey]) {
     [self setTitle:title];
   }
   [self setDrawsContentsIntoWindowFrame:[[aState objectForKey:kStateDrawsContentsIntoWindowFrameKey] boolValue]];
-  [self setTitlebarColor:[aState objectForKey:kStateActiveTitlebarColorKey] forActiveWindow:YES];
-  [self setTitlebarColor:[aState objectForKey:kStateInactiveTitlebarColorKey] forActiveWindow:NO];
   [self setShowsToolbarButton:[[aState objectForKey:kStateShowsToolbarButton] boolValue]];
   [self setCollectionBehavior:[[aState objectForKey:kStateCollectionBehavior] unsignedIntValue]];
 }
 
 - (NSMutableDictionary*)exportState
 {
   NSMutableDictionary* state = [NSMutableDictionary dictionaryWithCapacity:10];
   if (NSString* title = [self title]) {
     [state setObject:title forKey:kStateTitleKey];
   }
   [state setObject:[NSNumber numberWithBool:[self drawsContentsIntoWindowFrame]]
             forKey:kStateDrawsContentsIntoWindowFrameKey];
-  NSColor* activeTitlebarColor = [self titlebarColorForActiveWindow:YES];
-  if (activeTitlebarColor) {
-    [state setObject:activeTitlebarColor forKey:kStateActiveTitlebarColorKey];
-  }
-  NSColor* inactiveTitlebarColor = [self titlebarColorForActiveWindow:NO];
-  if (inactiveTitlebarColor) {
-    [state setObject:inactiveTitlebarColor forKey:kStateInactiveTitlebarColorKey];
-  }
   [state setObject:[NSNumber numberWithBool:[self showsToolbarButton]]
             forKey:kStateShowsToolbarButton];
   [state setObject:[NSNumber numberWithUnsignedInt: [self collectionBehavior]]
             forKey:kStateCollectionBehavior];
   return state;
 }
 
 - (void)setDrawsContentsIntoWindowFrame:(BOOL)aState
@@ -3273,34 +3219,16 @@ static const NSString* kStateCollectionB
   [[self standardWindowButton:NSWindowFullScreenButton] setNeedsDisplay:YES];
 }
 
 - (BOOL)useBrightTitlebarForeground
 {
   return mBrightTitlebarForeground;
 }
 
-// Pass nil here to get the default appearance.
-- (void)setTitlebarColor:(NSColor*)aColor forActiveWindow:(BOOL)aActive
-{
-  [aColor retain];
-  if (aActive) {
-    [mActiveTitlebarColor release];
-    mActiveTitlebarColor = aColor;
-  } else {
-    [mInactiveTitlebarColor release];
-    mInactiveTitlebarColor = aColor;
-  }
-}
-
-- (NSColor*)titlebarColorForActiveWindow:(BOOL)aActive
-{
-  return aActive ? mActiveTitlebarColor : mInactiveTitlebarColor;
-}
-
 - (NSView*)trackingAreaView
 {
   NSView* contentView = [self contentView];
   return [contentView superview] ? [contentView superview] : contentView;
 }
 
 - (ChildView*)mainChildView
 {
@@ -3575,22 +3503,16 @@ static const NSString* kStateCollectionB
     [self setAutorecalculatesContentBorderThickness:NO forEdge:NSMaxYEdge];
     [self setContentBorderThickness:0.0f forEdge:NSMaxYEdge];
   }
   return self;
 
   NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
 }
 
-- (void)setTitlebarColor:(NSColor*)aColor forActiveWindow:(BOOL)aActive
-{
-  [super setTitlebarColor:aColor forActiveWindow:aActive];
-  [self setTitlebarNeedsDisplayInRect:[self titlebarRect]];
-}
-
 - (void)setTitlebarNeedsDisplayInRect:(NSRect)aRect
 {
   [self setTitlebarNeedsDisplayInRect:aRect sync:NO];
 }
 
 - (void)setTitlebarNeedsDisplayInRect:(NSRect)aRect sync:(BOOL)aSync
 {
   NSRect titlebarRect = [self titlebarRect];

--- a/widget/nsBaseWidget.h
+++ b/widget/nsBaseWidget.h
@@ -251,18 +251,16 @@ public:
   virtual LayoutDeviceIntPoint GetClientOffset() override;
   virtual void            EnableDragDrop(bool aEnable) override {};
   virtual nsresult        AsyncEnableDragDrop(bool aEnable) override;
   virtual MOZ_MUST_USE nsresult
                           GetAttention(int32_t aCycleCount) override
                           { return NS_OK; }
   virtual bool            HasPendingInputEvent() override;
   virtual void            SetIcon(const nsAString &aIconSpec) override {}
-  virtual void            SetWindowTitlebarColor(nscolor aColor, bool aActive)
-                            override {}
   virtual void            SetDrawsInTitlebar(bool aState) override {}
   virtual bool            ShowsResizeIndicator(LayoutDeviceIntRect* aResizerRect) override;
   virtual void            FreeNativeData(void * data, uint32_t aDataType) override {}
   virtual MOZ_MUST_USE nsresult
                           BeginResizeDrag(mozilla::WidgetGUIEvent* aEvent,
                                           int32_t aHorizontal,
                                           int32_t aVertical) override
                           { return NS_ERROR_NOT_IMPLEMENTED; }

--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -1447,34 +1447,16 @@ class nsIWidget : public nsISupports
 
     /**
      * Ask whether there user input events pending.  All input events are
      * included, including those not targeted at this nsIwidget instance.
      */
     virtual bool HasPendingInputEvent() = 0;
 
     /**
-     * Set the background color of the window titlebar for this widget. On Mac,
-     * for example, this will remove the grey gradient and bottom border and
-     * instead show a single, solid color.
-     *
-     * Ignored on any platform that does not support it. Ignored by widgets that
-     * do not represent windows.
-     *
-     * @param aColor  The color to set the title bar background to. Alpha values
-     *                other than fully transparent (0) are respected if possible
-     *                on the platform. An alpha of 0 will cause the window to
-     *                draw with the default style for the platform.
-     *
-     * @param aActive Whether the color should be applied to active or inactive
-     *                windows.
-     */
-    virtual void SetWindowTitlebarColor(nscolor aColor, bool aActive) = 0;
-
-    /**
      * If set to true, the window will draw its contents into the titlebar
      * instead of below it.
      *
      * Ignored on any platform that does not support it. Ignored by widgets that
      * do not represent windows.
      * May result in a resize event, so should only be called from places where
      * reflow and painting is allowed.
      *