--- a/gfx/layers/ipc/CompositorBridgeChild.cpp
+++ b/gfx/layers/ipc/CompositorBridgeChild.cpp
@@ -472,18 +472,17 @@ CompositorBridgeChild::RecvUpdatePluginC
         widget->Resize(aContentOffset.x + bounds.x,
                        aContentOffset.y + bounds.y,
                        bounds.width, bounds.height, true);
       }
 
       widget->Enable(isVisible);
 
       // visible state - updated after clipping, prior to invalidating
-      rv = widget->Show(isVisible);
-      NS_ASSERTION(NS_SUCCEEDED(rv), "widget call failure");
+      widget->Show(isVisible);
 
       // Handle invalidation, this can be costly, avoid if it is not needed.
       if (isVisible) {
         // invalidate region (widget origin)
 #if defined(XP_WIN)
         // Work around for flash's crummy sandbox. See bug 762948. This call
         // digs down into the window hirearchy, invalidating regions on
         // windows owned by other processes.

--- a/gfx/tests/gtest/TestCompositor.cpp
+++ b/gfx/tests/gtest/TestCompositor.cpp
@@ -61,17 +61,17 @@ public:
   virtual nsresult        Create(nsIWidget* aParent,
                                  nsNativeWidget aNativeParent,
                                  const LayoutDeviceIntRect& aRect,
                                  nsWidgetInitData* aInitData = nullptr) override { return NS_OK; }
   virtual nsresult        Create(nsIWidget* aParent,
                                  nsNativeWidget aNativeParent,
                                  const DesktopIntRect& aRect,
                                  nsWidgetInitData* aInitData = nullptr) override { return NS_OK; }
-  NS_IMETHOD              Show(bool aState) override { return NS_OK; }
+  virtual void            Show(bool aState) override {}
   virtual bool            IsVisible() const override { return true; }
   virtual void            Move(double aX, double aY) override {}
   virtual void            Resize(double aWidth, double aHeight, bool aRepaint) override {}
   virtual void            Resize(double aX, double aY,
                                  double aWidth, double aHeight, bool aRepaint) override {}
 
   virtual void            Enable(bool aState) override {}
   virtual bool            IsEnabled() const override { return true; }

--- a/widget/PuppetWidget.cpp
+++ b/widget/PuppetWidget.cpp
@@ -185,17 +185,17 @@ PuppetWidget::Destroy()
   mChild = nullptr;
   if (mLayerManager) {
     mLayerManager->Destroy();
   }
   mLayerManager = nullptr;
   mTabChild = nullptr;
 }
 
-NS_IMETHODIMP
+void
 PuppetWidget::Show(bool aState)
 {
   NS_ASSERTION(mEnabled,
                "does it make sense to Show()/Hide() a disabled widget?");
 
   bool wasVisible = mVisible;
   mVisible = aState;
 
@@ -211,18 +211,16 @@ PuppetWidget::Show(bool aState)
     // PuppetWidget was hidden, those layers are dropped,
     // so the previously attached widget listener is really
     // of no use anymore (and is actually actively harmful - see
     // bug 1323586).
     mPreviouslyAttachedWidgetListener = nullptr;
     Resize(mBounds.width, mBounds.height, false);
     Invalidate(mBounds);
   }
-
-  return NS_OK;
 }
 
 void
 PuppetWidget::Resize(double aWidth,
                      double aHeight,
                      bool   aRepaint)
 {
   LayoutDeviceIntRect oldBounds = mBounds;

--- a/widget/PuppetWidget.h
+++ b/widget/PuppetWidget.h
@@ -73,17 +73,17 @@ public:
 
   virtual already_AddRefed<nsIWidget>
   CreateChild(const LayoutDeviceIntRect& aRect,
               nsWidgetInitData* aInitData = nullptr,
               bool aForceUseIWidgetParent = false) override;
 
   virtual void Destroy() override;
 
-  NS_IMETHOD Show(bool aState) override;
+  virtual void Show(bool aState) override;
 
   virtual bool IsVisible() const override
   { return mVisible; }
 
   virtual void ConstrainPosition(bool     /*ignored aAllowSlop*/,
                                  int32_t* aX,
                                  int32_t* aY) override
   { *aX = kMaxDimension; *aY = kMaxDimension; }

--- a/widget/android/nsWindow.cpp
+++ b/widget/android/nsWindow.cpp
@@ -1672,28 +1672,28 @@ nsWindow::GetDefaultScaleInternal()
 {
 
     nsCOMPtr<nsIScreen> screen = GetWidgetScreen();
     MOZ_ASSERT(screen);
     RefPtr<nsScreenAndroid> screenAndroid = (nsScreenAndroid*) screen.get();
     return screenAndroid->GetDensity();
 }
 
-NS_IMETHODIMP
+void
 nsWindow::Show(bool aState)
 {
     ALOG("nsWindow[%p]::Show %d", (void*)this, aState);
 
     if (mWindowType == eWindowType_invisible) {
         ALOG("trying to show invisible window! ignoring..");
-        return NS_ERROR_FAILURE;
+        return;
     }
 
     if (aState == mIsVisible)
-        return NS_OK;
+        return;
 
     mIsVisible = aState;
 
     if (IsTopLevel()) {
         // XXX should we bring this to the front when it's shown,
         // if it's a toplevel widget?
 
         // XXX we should synthesize a eMouseExitFromWidget (for old top
@@ -1719,18 +1719,16 @@ nsWindow::Show(bool aState)
         }
     } else if (FindTopLevel() == nsWindow::TopWindow()) {
         RedrawAll();
     }
 
 #ifdef DEBUG_ANDROID_WIDGET
     DumpWindows();
 #endif
-
-    return NS_OK;
 }
 
 bool
 nsWindow::IsVisible() const
 {
     return mIsVisible;
 }
 

--- a/widget/android/nsWindow.h
+++ b/widget/android/nsWindow.h
@@ -157,17 +157,17 @@ public:
                                          const LayoutDeviceIntRect& aRect,
                                          nsWidgetInitData* aInitData) override;
     virtual void Destroy() override;
     NS_IMETHOD ConfigureChildren(const nsTArray<nsIWidget::Configuration>&) override;
     virtual void SetParent(nsIWidget* aNewParent) override;
     virtual nsIWidget *GetParent(void) override;
     virtual float GetDPI() override;
     virtual double GetDefaultScaleInternal() override;
-    NS_IMETHOD Show(bool aState) override;
+    virtual void Show(bool aState) override;
     virtual bool IsVisible() const override;
     virtual void ConstrainPosition(bool aAllowSlop,
                                    int32_t *aX,
                                    int32_t *aY) override;
     virtual void Move(double aX,
                       double aY) override;
     virtual void Resize(double aWidth,
                         double aHeight,

--- a/widget/cocoa/nsChildView.h
+++ b/widget/cocoa/nsChildView.h
@@ -303,17 +303,17 @@ public:
   virtual MOZ_MUST_USE nsresult Create(nsIWidget* aParent,
                                        nsNativeWidget aNativeParent,
                                        const LayoutDeviceIntRect& aRect,
                                        nsWidgetInitData* aInitData = nullptr)
                                        override;
 
   virtual void            Destroy() override;
 
-  NS_IMETHOD              Show(bool aState) override;
+  virtual void            Show(bool aState) override;
   virtual bool            IsVisible() const override;
 
   virtual void            SetParent(nsIWidget* aNewParent) override;
   virtual nsIWidget*      GetParent(void) override;
   virtual float           GetDPI() override;
 
   virtual void            Move(double aX, double aY) override;
   virtual void            Resize(double aWidth, double aHeight, bool aRepaint) override;

--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -712,35 +712,35 @@ ManipulateViewWithoutNeedingDisplay(NSVi
     win = (BaseWindow*)[aView window];
   }
   [win disableSetNeedsDisplay];
   aCallback();
   [win enableSetNeedsDisplay];
 }
 
 // Hide or show this component
-NS_IMETHODIMP nsChildView::Show(bool aState)
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
+void
+nsChildView::Show(bool aState)
+{
+  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
   if (aState != mVisible) {
     // Provide an autorelease pool because this gets called during startup
     // on the "hidden window", resulting in cocoa object leakage if there's
     // no pool in place.
     nsAutoreleasePool localPool;
 
     ManipulateViewWithoutNeedingDisplay(mView, ^{
       [mView setHidden:!aState];
     });
 
     mVisible = aState;
   }
-  return NS_OK;
-
-  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
+
+  NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
 // Change the parent of this widget
 void
 nsChildView::SetParent(nsIWidget* aNewParent)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 

--- a/widget/cocoa/nsCocoaWindow.h
+++ b/widget/cocoa/nsCocoaWindow.h
@@ -232,17 +232,17 @@ public:
     virtual MOZ_MUST_USE nsresult Create(nsIWidget* aParent,
                                          nsNativeWidget aNativeParent,
                                          const LayoutDeviceIntRect& aRect,
                                          nsWidgetInitData* aInitData = nullptr)
                                          override;
 
     virtual void            Destroy() override;
 
-    NS_IMETHOD              Show(bool aState) override;
+    virtual void            Show(bool aState) override;
     virtual nsIWidget*      GetSheetWindowParent(void) override;
     virtual void            Enable(bool aState) override;
     virtual bool            IsEnabled() const override;
     virtual void            SetModal(bool aState) override;
     virtual void            SetFakeModal(bool aState) override;
     virtual bool            IsRunningAppModal() override;
     virtual bool            IsVisible() const override;
     NS_IMETHOD              SetFocus(bool aState=false) override;

--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -728,56 +728,57 @@ nsCocoaWindow::SetFakeModal(bool aState)
 
 bool
 nsCocoaWindow::IsRunningAppModal()
 {
   return [NSApp _isRunningAppModal];
 }
 
 // Hide or show this window
-NS_IMETHODIMP nsCocoaWindow::Show(bool bState)
+void
+nsCocoaWindow::Show(bool bState)
 {
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
+  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
   if (!mWindow)
-    return NS_OK;
+    return;
 
   // We need to re-execute sometimes in order to bring already-visible
   // windows forward.
   if (!mSheetNeedsShow && !bState && ![mWindow isVisible])
-    return NS_OK;
+    return;
 
   // Protect against re-entering.
   if (bState && [mWindow isBeingShown])
-    return NS_OK;
+    return;
 
   [mWindow setBeingShown:bState];
 
   nsIWidget* parentWidget = mParent;
   nsCOMPtr<nsPIWidgetCocoa> piParentWidget(do_QueryInterface(parentWidget));
   NSWindow* nativeParentWindow = (parentWidget) ?
     (NSWindow*)parentWidget->GetNativeData(NS_NATIVE_WINDOW) : nil;
 
   if (bState && !mBounds.IsEmpty()) {
     // Don't try to show a popup when the parent isn't visible or is minimized.
     if (mWindowType == eWindowType_popup && nativeParentWindow) {
       if (![nativeParentWindow isVisible] || [nativeParentWindow isMiniaturized]) {
-        return NS_OK;
+        return;
       }
     }
 
     if (mPopupContentView) {
       // Ensure our content view is visible. We never need to hide it.
       mPopupContentView->Show(true);
     }
 
     if (mWindowType == eWindowType_sheet) {
       // bail if no parent window (its basically what we do in Carbon)
       if (!nativeParentWindow || !piParentWidget)
-        return NS_ERROR_FAILURE;
+        return;
 
       NSWindow* topNonSheetWindow = nativeParentWindow;
       
       // If this sheet is the child of another sheet, hide the parent so that
       // this sheet can be displayed. Leave the parent mSheetNeedsShow alone,
       // that is only used to handle sibling sheet contention. The parent will
       // return once there are no more child sheets.
       bool parentIsSheet = false;
@@ -978,19 +979,17 @@ NS_IMETHODIMP nsCocoaWindow::Show(bool b
           postNotificationName:@"com.apple.HIToolbox.endMenuTrackingNotification"
                         object:@"org.mozilla.gecko.PopupWindow"];
       }
     }
   }
 
   [mWindow setBeingShown:NO];
 
-  return NS_OK;
-
-  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
+  NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
 struct ShadowParams {
   float standardDeviation;
   float density;
   int offsetX;
   int offsetY;
   unsigned int flags;
@@ -1333,19 +1332,18 @@ nsCocoaWindow::HideWindowChrome(bool aSh
   while ((child = [enumerator nextObject])) {
     [mWindow addChildWindow:child ordered:NSWindowAbove];
   }
 
   // Show the new window.
   if (isVisible) {
     bool wasAnimationSuppressed = mIsAnimationSuppressed;
     mIsAnimationSuppressed = true;
-    rv = Show(true);
+    Show(true);
     mIsAnimationSuppressed = wasAnimationSuppressed;
-    NS_ENSURE_SUCCESS_VOID(rv);
   }
 
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
 class FullscreenTransitionData : public nsISupports
 {
 public:

--- a/widget/gonk/nsWindow.cpp
+++ b/widget/gonk/nsWindow.cpp
@@ -340,48 +340,49 @@ nsWindow::Destroy()
     mOnDestroyCalled = true;
     mScreen->UnregisterWindow(this);
     if (this == gFocusedWindow) {
         gFocusedWindow = nullptr;
     }
     nsBaseWidget::OnDestroy();
 }
 
-NS_IMETHODIMP
+void
 nsWindow::Show(bool aState)
 {
     if (mWindowType == eWindowType_invisible) {
-        return NS_OK;
+        return;
     }
 
     if (mVisible == aState) {
-        return NS_OK;
+        return;
     }
 
     mVisible = aState;
     if (!IS_TOPLEVEL()) {
-        return mParent ? mParent->Show(aState) : NS_OK;
+        if (mParent) {
+            mParent->Show(aState);
+        }
+        return;
     }
 
     if (aState) {
         BringToTop();
     } else {
         const nsTArray<nsWindow*>& windows =
             mScreen->GetTopWindows();
         for (unsigned int i = 0; i < windows.Length(); i++) {
             nsWindow *win = windows[i];
             if (!win->mVisible) {
                 continue;
             }
             win->BringToTop();
             break;
         }
     }
-
-    return NS_OK;
 }
 
 bool
 nsWindow::IsVisible() const
 {
     return mVisible;
 }
 

--- a/widget/gonk/nsWindow.h
+++ b/widget/gonk/nsWindow.h
@@ -49,17 +49,17 @@ public:
 
     using nsBaseWidget::Create; // for Create signature not overridden here
     virtual MOZ_MUST_USE nsresult Create(nsIWidget* aParent,
                                          void* aNativeParent,
                                          const LayoutDeviceIntRect& aRect,
                                          nsWidgetInitData* aInitData) override;
     virtual void Destroy();
 
-    NS_IMETHOD Show(bool aState);
+    virtual void Show(bool aState);
     virtual bool IsVisible() const;
     virtual void Move(double aX,
                       double aY);
     virtual void Resize(double aWidth,
                         double aHeight,
                         bool  aRepaint);
     virtual void Resize(double aX,
                         double aY,

--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -1057,21 +1057,21 @@ void nsWindow::SetSizeConstraints(const 
             LayoutDeviceIntSize(NS_MAXSIZE, NS_MAXSIZE)) {
             hints |= GDK_HINT_MAX_SIZE;
         }
         gtk_window_set_geometry_hints(GTK_WINDOW(mShell), nullptr,
                                       &geometry, GdkWindowHints(hints));
     }
 }
 
-NS_IMETHODIMP
+void
 nsWindow::Show(bool aState)
 {
     if (aState == mIsShown)
-        return NS_OK;
+        return;
 
     // Clear our cached resources when the window is hidden.
     if (mIsShown && !aState) {
         ClearCachedResources();
     }
 
     mIsShown = aState;
 
@@ -1084,31 +1084,29 @@ nsWindow::Show(bool aState)
     }
 
     // Ok, someone called show on a window that isn't sized to a sane
     // value.  Mark this window as needing to have Show() called on it
     // and return.
     if ((aState && !AreBoundsSane()) || !mCreated) {
         LOG(("\tbounds are insane or window hasn't been created yet\n"));
         mNeedsShow = true;
-        return NS_OK;
+        return;
     }
 
     // If someone is hiding this widget, clear any needing show flag.
     if (!aState)
         mNeedsShow = false;
 
 #ifdef ACCESSIBILITY
     if (aState && a11y::ShouldA11yBeEnabled())
         CreateRootAccessible();
 #endif
 
     NativeShow(aState);
-
-    return NS_OK;
 }
 
 void
 nsWindow::Resize(double aWidth, double aHeight, bool aRepaint)
 {
     double scale = BoundsUseDesktopPixels() ? GetDesktopToDeviceScale().scale : 1.0;
     int32_t width = NSToIntRound(scale * aWidth);
     int32_t height = NSToIntRound(scale * aHeight);

--- a/widget/gtk/nsWindow.h
+++ b/widget/gtk/nsWindow.h
@@ -111,17 +111,17 @@ public:
     virtual void       SetModal(bool aModal) override;
     virtual bool       IsVisible() const override;
     virtual void       ConstrainPosition(bool aAllowSlop,
                                          int32_t *aX,
                                          int32_t *aY) override;
     virtual void       SetSizeConstraints(const SizeConstraints& aConstraints) override;
     virtual void       Move(double aX,
                             double aY) override;
-    NS_IMETHOD         Show             (bool aState) override;
+    virtual void       Show             (bool aState) override;
     virtual void       Resize           (double aWidth,
                                          double aHeight,
                                          bool   aRepaint) override;
     virtual void       Resize           (double aX,
                                          double aY,
                                          double aWidth,
                                          double aHeight,
                                          bool   aRepaint) override;

--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -631,17 +631,17 @@ class nsIWidget : public nsISupports
     }
 
     /**
      * Show or hide this widget
      *
      * @param aState true to show the Widget, false to hide it
      *
      */
-    NS_IMETHOD Show(bool aState) = 0;
+    virtual void Show(bool aState) = 0;
 
     /**
      * Make the window modal.
      */
     virtual void SetModal(bool aModal) = 0;
 
     /**
      * Make the non-modal window opened by modal window fake-modal, that will

--- a/widget/uikit/nsWindow.h
+++ b/widget/uikit/nsWindow.h
@@ -30,17 +30,17 @@ public:
     //
 
     virtual MOZ_MUST_USE nsresult Create(nsIWidget* aParent,
                                          nsNativeWidget aNativeParent,
                                          const LayoutDeviceIntRect& aRect,
                                          nsWidgetInitData* aInitData = nullptr)
                                          override;
     virtual void Destroy() override;
-    NS_IMETHOD Show(bool aState) override;
+    virtual void Show(bool aState) override;
     virtual void            Enable(bool aState) override {}
     virtual bool            IsEnabled() const override {
         return true;
     }
     virtual bool            IsVisible() const override {
         return mVisible;
     }
     NS_IMETHOD              SetFocus(bool aState=false) override;

--- a/widget/uikit/nsWindow.mm
+++ b/widget/uikit/nsWindow.mm
@@ -553,29 +553,28 @@ nsWindow::ConfigureChildren(const nsTArr
                          config[i].mBounds.width,
                          config[i].mBounds.height,
                          false);
     }
 
     return NS_OK;
 }
 
-NS_IMETHODIMP
+void
 nsWindow::Show(bool aState)
 {
   if (aState != mVisible) {
       mNativeView.hidden = aState ? NO : YES;
       if (aState) {
           UIView* parentView = mParent ? mParent->mNativeView : nsAppShell::gWindow.rootViewController.view;
           [parentView bringSubviewToFront:mNativeView];
           [mNativeView setNeedsDisplay];
       }
       mVisible = aState;
   }
-  return NS_OK;
 }
 
 void
 nsWindow::Move(double aX, double aY)
 {
   if (!mNativeView || (mBounds.x == aX && mBounds.y == aY))
     return;
 

--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -1415,17 +1415,18 @@ nsWindow::GetFallbackScrollSnapshot(cons
 /**************************************************************
  *
  * SECTION: nsIWidget::Show
  *
  * Hide or show this component.
  *
  **************************************************************/
 
-NS_IMETHODIMP nsWindow::Show(bool bState)
+void
+nsWindow::Show(bool bState)
 {
   if (mWindowType == eWindowType_popup) {
     // See bug 603793. When we try to draw D3D9/10 windows with a drop shadow
     // without the DWM on a secondary monitor, windows fails to composite
     // our windows correctly. We therefor switch off the drop shadow for
     // pop-up windows when the DWM is disabled and two monitors are
     // connected.
     if (HasBogusPopupsDropShadowOnMultiMonitor() &&
@@ -1530,27 +1531,25 @@ NS_IMETHODIMP nsWindow::Show(bool bState
       if (mWindowType != eWindowType_dialog) {
         ::ShowWindow(mWnd, SW_HIDE);
       } else {
         ::SetWindowPos(mWnd, 0, 0, 0, 0, 0, SWP_HIDEWINDOW | SWP_NOSIZE | SWP_NOMOVE |
                        SWP_NOZORDER | SWP_NOACTIVATE);
       }
     }
   }
-  
+
 #ifdef MOZ_XUL
   if (!wasVisible && bState) {
     Invalidate();
     if (syncInvalidate && !mInDtor && !mOnDestroyCalled) {
       ::UpdateWindow(mWnd);
     }
   }
 #endif
-
-  return NS_OK;
 }
 
 /**************************************************************
  *
  * SECTION: nsIWidget::IsVisible
  *
  * Returns the visibility state.
  *

--- a/widget/windows/nsWindow.h
+++ b/widget/windows/nsWindow.h
@@ -114,17 +114,17 @@ public:
   {
     if (mozilla::widget::WinUtils::IsPerMonitorDPIAware()) {
       return mozilla::DesktopToLayoutDeviceScale(1.0);
     } else {
       return mozilla::DesktopToLayoutDeviceScale(GetDefaultScaleInternal());
     }
   }
 
-  NS_IMETHOD              Show(bool bState) override;
+  virtual void            Show(bool aState) override;
   virtual bool            IsVisible() const override;
   virtual void            ConstrainPosition(bool aAllowSlop, int32_t *aX, int32_t *aY) override;
   virtual void            SetSizeConstraints(const SizeConstraints& aConstraints) override;
   virtual const SizeConstraints GetSizeConstraints() override;
   virtual void            Move(double aX, double aY) override;
   virtual void            Resize(double aWidth, double aHeight, bool aRepaint) override;
   virtual void            Resize(double aX, double aY, double aWidth, double aHeight, bool aRepaint) override;
   virtual MOZ_MUST_USE nsresult