diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 058ef3444aa..65a1f677ef1 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -7488,7 +7488,7 @@ PresShell::DoReflow(nsIFrame* target, bool aInterruptible)
                                              target->GetView(),
                                              boundsRelativeToTarget);
   nsContainerFrame::SyncWindowProperties(mPresContext, target,
-                                         target->GetView());
+                                         target->GetView(), rcx);
 
   target->DidReflow(mPresContext, nullptr, NS_FRAME_REFLOW_FINISHED);
   if (target == rootFrame && size.height == NS_UNCONSTRAINEDSIZE) {
diff --git a/layout/generic/nsContainerFrame.cpp b/layout/generic/nsContainerFrame.cpp
index d5e581494d4..ebd0dd4a51f 100644
--- a/layout/generic/nsContainerFrame.cpp
+++ b/layout/generic/nsContainerFrame.cpp
@@ -34,6 +34,8 @@
 #include "nsListControlFrame.h"
 #include "nsIBaseWindow.h"
 #include "nsThemeConstants.h"
+#include "nsBoxLayoutState.h"
+#include "nsRenderingContext.h"
 #include "nsCSSFrameConstructor.h"
 #include "mozilla/dom/Element.h"
 
@@ -632,7 +634,8 @@ IsTopLevelWidget(nsIWidget* aWidget)
 void
 nsContainerFrame::SyncWindowProperties(nsPresContext*       aPresContext,
                                        nsIFrame*            aFrame,
-                                       nsIView*             aView)
+                                       nsIView*             aView,
+                                       nsRenderingContext*  aRC)
 {
 #ifdef MOZ_XUL
   if (!aView || !nsCSSRendering::IsCanvasFrame(aFrame) || !aView->HasWidget())
@@ -676,9 +679,47 @@ nsContainerFrame::SyncWindowProperties(nsPresContext*       aPresContext,
   nsIWidget* viewWidget = aView->GetWidget();
   viewWidget->SetTransparencyMode(mode);
   windowWidget->SetWindowShadowStyle(rootFrame->GetStyleUIReset()->mWindowShadow);
+
+  if (!aRC)
+    return;
+  
+  nsBoxLayoutState aState(aPresContext, aRC);
+  nsSize minSize = rootFrame->GetMinSize(aState);
+  nsSize maxSize = rootFrame->GetMaxSize(aState);
+
+  SetSizeConstraints(aPresContext, windowWidget, minSize, maxSize);
 #endif
 }
 
+void nsContainerFrame::SetSizeConstraints(nsPresContext* aPresContext,
+                                          nsIWidget* aWidget,
+                                          const nsSize& aMinSize,
+                                          const nsSize& aMaxSize)
+{
+  nsIntSize devMinSize(aPresContext->AppUnitsToDevPixels(aMinSize.width),
+                       aPresContext->AppUnitsToDevPixels(aMinSize.height));
+  nsIntSize devMaxSize(aMaxSize.width == NS_INTRINSICSIZE ? NS_MAXSIZE :
+                         aPresContext->AppUnitsToDevPixels(aMaxSize.width),
+                       aMaxSize.height == NS_INTRINSICSIZE ? NS_MAXSIZE :
+                         aPresContext->AppUnitsToDevPixels(aMaxSize.height));
+  widget::SizeConstraints constraints(devMinSize, devMaxSize);
+
+  // The sizes are in inner window sizes, so convert them into outer window sizes.
+  // Use a size of (200, 200) as only the difference between the inner and outer
+  // size is needed.
+  nsIntSize windowSize = aWidget->ClientToWindowSize(nsIntSize(200, 200));
+  if (constraints.mMinSize.width)
+    constraints.mMinSize.width += windowSize.width - 200;
+  if (constraints.mMinSize.height)
+    constraints.mMinSize.height += windowSize.height - 200;
+  if (constraints.mMaxSize.width != NS_MAXSIZE)
+    constraints.mMaxSize.width += windowSize.width - 200;
+  if (constraints.mMaxSize.height != NS_MAXSIZE)
+    constraints.mMaxSize.height += windowSize.height - 200;
+
+  aWidget->SetSizeConstraints(constraints);
+}
+
 void
 nsContainerFrame::SyncFrameViewAfterReflow(nsPresContext* aPresContext,
                                            nsIFrame*       aFrame,
diff --git a/layout/generic/nsContainerFrame.h b/layout/generic/nsContainerFrame.h
index 96f996c81de..b1473f21f34 100644
--- a/layout/generic/nsContainerFrame.h
+++ b/layout/generic/nsContainerFrame.h
@@ -141,7 +141,8 @@ public:
   // shadow.
   static void SyncWindowProperties(nsPresContext*       aPresContext,
                                    nsIFrame*            aFrame,
-                                   nsIView*             aView);
+                                   nsIView*             aView,
+                                   nsRenderingContext*  aRC = nullptr);
 
   // Sets the view's attributes from the frame style.
   // - visibility
@@ -155,6 +156,20 @@ public:
                                       nsIView*         aView,
                                       PRUint32         aFlags = 0);
 
+  /**
+   * Converts the minimum and maximum sizes given in inner window app units to
+   * outer window device pixel sizes and assigns these constraints to the widget.
+   *
+   * @param aPresContext pres context
+   * @param aWidget widget for this frame
+   * @param minimum size of the window in app units
+   * @param maxmimum size of the window in app units
+   */
+  static void SetSizeConstraints(nsPresContext* aPresContext,
+                                 nsIWidget* aWidget,
+                                 const nsSize& aMinSize,
+                                 const nsSize& aMaxSize);
+
   // Used by both nsInlineFrame and nsFirstLetterFrame.
   void DoInlineIntrinsicWidth(nsRenderingContext *aRenderingContext,
                               InlineIntrinsicWidthData *aData,
diff --git a/layout/xul/base/src/nsMenuPopupFrame.cpp b/layout/xul/base/src/nsMenuPopupFrame.cpp
index b052908cff8..4271875f161 100644
--- a/layout/xul/base/src/nsMenuPopupFrame.cpp
+++ b/layout/xul/base/src/nsMenuPopupFrame.cpp
@@ -450,6 +450,14 @@ nsMenuPopupFrame::LayoutPopup(nsBoxLayoutState& aState, nsIFrame* aParentMenu, b
     nsRect rect = GetRect();
     rect.x = rect.y = 0;
 
+    if (sizeChanged) {
+      // If the size of the popup changed, apply any size constraints.
+      nsIWidget* widget = view->GetWidget();
+      if (widget) {
+        SetSizeConstraints(pc, widget, minSize, maxSize);
+      }
+    }
+
     viewManager->ResizeView(view, rect);
 
     viewManager->SetViewVisibility(view, nsViewVisibility_kShow);
diff --git a/layout/xul/base/src/nsResizerFrame.cpp b/layout/xul/base/src/nsResizerFrame.cpp
index aaf9dac60db..6d2647d7abe 100644
--- a/layout/xul/base/src/nsResizerFrame.cpp
+++ b/layout/xul/base/src/nsResizerFrame.cpp
@@ -29,6 +29,7 @@
 #include "mozilla/dom/Element.h"
 #include "nsContentErrors.h"
 
+using namespace mozilla;
 
 //
 // NS_NewResizerFrame
@@ -186,8 +187,19 @@ nsResizerFrame::HandleEvent(nsPresContext* aPresContext,
       }
 
       nsIntRect rect = mMouseDownRect;
-      AdjustDimensions(&rect.x, &rect.width, mouseMove.x, direction.mHorizontal);
-      AdjustDimensions(&rect.y, &rect.height, mouseMove.y, direction.mVertical);
+
+      // Check if there are any size constraints on this window.
+      widget::SizeConstraints sizeConstraints;
+      if (window) {
+        nsCOMPtr<nsIWidget> widget;
+        window->GetMainWidget(getter_AddRefs(widget));
+        sizeConstraints = widget->GetSizeConstraints();
+      }
+
+      AdjustDimensions(&rect.x, &rect.width, sizeConstraints.mMinSize.width,
+                       sizeConstraints.mMaxSize.width, mouseMove.x, direction.mHorizontal);
+      AdjustDimensions(&rect.y, &rect.height, sizeConstraints.mMinSize.height,
+                       sizeConstraints.mMaxSize.height, mouseMove.y, direction.mVertical);
 
       // Don't allow resizing a window or a popup past the edge of the screen,
       // so adjust the rectangle to fit within the available screen area.
@@ -249,6 +261,10 @@ nsResizerFrame::HandleEvent(nsPresContext* aPresContext,
         ResizeContent(contentToResize, direction, sizeInfo, &originalSizeInfo);
         MaybePersistOriginalSize(contentToResize, originalSizeInfo);
 
+        // Move the popup to the new location unless it is anchored, since
+        // the position shouldn't change. nsMenuPopupFrame::SetPopupPosition
+        // will instead ensure that the popup's position is anchored at the
+        // right place.
         if (weakFrame.IsAlive() &&
             (oldRect.x != rect.x || oldRect.y != rect.y) &&
             (!menuPopupFrame->IsAnchored() ||
@@ -365,25 +381,25 @@ nsResizerFrame::GetContentToResize(nsIPresShell* aPresShell, nsIBaseWindow** aWi
   return aPresShell->GetDocument()->GetElementById(elementid);
 }
 
-/* adjust the window position and size according to the mouse movement and
- * the resizer direction
- */
 void
 nsResizerFrame::AdjustDimensions(PRInt32* aPos, PRInt32* aSize,
+                                 PRInt32 aMinSize, PRInt32 aMaxSize,
                                  PRInt32 aMovement, PRInt8 aResizerDirection)
 {
-  switch(aResizerDirection)
-  {
-    case -1:
-      // only move the window when the direction is top and/or left
-      *aPos+= aMovement;
-      // falling through: the window is resized in both cases
-    case 1:
-      *aSize+= aResizerDirection*aMovement;
-      // use one as a minimum size or the element could disappear
-      if (*aSize < 1)
-        *aSize = 1;
-  }
+  PRInt32 oldSize = *aSize;
+
+  *aSize += aResizerDirection * aMovement;
+  // use one as a minimum size or the element could disappear
+  if (*aSize < 1)
+    *aSize = 1;
+
+  // Constrain the size within the minimum and maximum size.
+  *aSize = NS_MAX(aMinSize, NS_MIN(aMaxSize, *aSize));
+
+  // For left and top resizers, the window must be moved left by the same
+  // amount that the window was resized.
+  if (aResizerDirection == -1)
+    *aPos += oldSize - *aSize;
 }
 
 /* static */ void
diff --git a/layout/xul/base/src/nsResizerFrame.h b/layout/xul/base/src/nsResizerFrame.h
index 330713b0a5b..ef5f0772d64 100644
--- a/layout/xul/base/src/nsResizerFrame.h
+++ b/layout/xul/base/src/nsResizerFrame.h
@@ -35,8 +35,22 @@ protected:
   nsIContent* GetContentToResize(nsIPresShell* aPresShell, nsIBaseWindow** aWindow);
 
   Direction GetDirection();
+
+  /**
+   * Adjust the window position and size in a direction according to the mouse
+   * movement and the resizer direction. The minimum and maximum size is used
+   * to constrain the size.
+   *
+   * @param aPos left or top position
+   * @param aSize width or height
+   * @param aMinSize minimum width or height
+   * @param aMacSize maximum width or height
+   * @param aMovement the amount the mouse was moved
+   * @param aResizerDirection resizer direction returned by GetDirection
+   */
   static void AdjustDimensions(PRInt32* aPos, PRInt32* aSize,
-                        PRInt32 aMovement, PRInt8 aResizerDirection);
+                               PRInt32 aMinSize, PRInt32 aMaxSize,
+                               PRInt32 aMovement, PRInt8 aResizerDirection);
 
   struct SizeInfo {
     nsString width, height;
diff --git a/widget/cocoa/nsCocoaWindow.h b/widget/cocoa/nsCocoaWindow.h
index b6baaa66019..6b71d71e052 100644
--- a/widget/cocoa/nsCocoaWindow.h
+++ b/widget/cocoa/nsCocoaWindow.h
@@ -224,6 +224,7 @@ public:
 
     NS_IMETHOD              ConstrainPosition(bool aAllowSlop,
                                               PRInt32 *aX, PRInt32 *aY);
+    virtual void            SetSizeConstraints(const SizeConstraints& aConstraints);
     NS_IMETHOD              Move(PRInt32 aX, PRInt32 aY);
     NS_IMETHOD              PlaceBehind(nsTopLevelWidgetZPlacement aPlacement,
                                         nsIWidget *aWidget, bool aActivate);
diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
index ac40789e817..8b74f8d448a 100644
--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -1072,6 +1072,32 @@ NS_IMETHODIMP nsCocoaWindow::ConstrainPosition(bool aAllowSlop,
   return NS_OK;
 }
 
+void nsCocoaWindow::SetSizeConstraints(const SizeConstraints& aConstraints)
+{
+  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
+
+  // Popups can be smaller than (60, 60)
+  NSRect rect =
+    (mWindowType == eWindowType_popup) ? NSZeroRect : NSMakeRect(0.0, 0.0, 60, 60);
+  rect = [mWindow frameRectForContentRect:rect];
+
+  SizeConstraints c = aConstraints;
+  c.mMinSize.width = NS_MAX(PRInt32(rect.size.width), c.mMinSize.width);
+  c.mMinSize.height = NS_MAX(PRInt32(rect.size.height), c.mMinSize.height);
+
+  NSSize minSize = { static_cast<CGFloat>(c.mMinSize.width),
+                     static_cast<CGFloat>(c.mMinSize.height) };
+  [mWindow setMinSize:minSize];
+
+  NSSize maxSize = { c.mMaxSize.width == NS_MAXSIZE ? FLT_MAX : c.mMaxSize.width,
+                     c.mMaxSize.height == NS_MAXSIZE ? FLT_MAX : c.mMaxSize.height };
+  [mWindow setMaxSize:maxSize];
+
+  nsBaseWidget::SetSizeConstraints(c);
+
+  NS_OBJC_END_TRY_ABORT_BLOCK;
+}
+
 NS_IMETHODIMP nsCocoaWindow::Move(PRInt32 aX, PRInt32 aY)
 {
   if (!mWindow || (mBounds.x == aX && mBounds.y == aY))
@@ -1250,6 +1276,8 @@ NS_IMETHODIMP nsCocoaWindow::Resize(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRIn
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
 
+  ConstrainSize(&aWidth, &aHeight);
+
   nsIntRect newBounds = nsIntRect(aX, aY, aWidth, aHeight);
   FitRectToVisibleAreaForScreen(newBounds, [mWindow screen]);
 
@@ -1617,11 +1645,6 @@ nsIntSize nsCocoaWindow::ClientToWindowSize(const nsIntSize& aClientSize)
   if (!mWindow)
     return nsIntSize(0, 0);
 
-  // this is only called for popups currently. If needed, expand this to support
-  // other types of windows
-  if (!IsPopupWithTitleBar())
-    return aClientSize;
-
   NSRect rect(NSMakeRect(0.0, 0.0, aClientSize.width, aClientSize.height));
 
   NSRect inflatedRect = [mWindow frameRectForContentRect:rect];
diff --git a/widget/gtk2/nsWindow.cpp b/widget/gtk2/nsWindow.cpp
index 7fbf461bb2a..722cef4eadb 100644
--- a/widget/gtk2/nsWindow.cpp
+++ b/widget/gtk2/nsWindow.cpp
@@ -944,6 +944,23 @@ nsWindow::ConstrainPosition(bool aAllowSlop, PRInt32 *aX, PRInt32 *aY)
     return NS_OK;
 }
 
+void nsWindow::SetSizeConstraints(const SizeConstraints& aConstraints)
+{
+  if (mShell) {
+    GdkGeometry geometry;
+    geometry.min_width = aConstraints.mMinSize.width;
+    geometry.min_height = aConstraints.mMinSize.height;
+    geometry.max_width = aConstraints.mMaxSize.width;
+    geometry.max_height = aConstraints.mMaxSize.height;
+
+    PRUint32 hints = GDK_HINT_MIN_SIZE | GDK_HINT_MAX_SIZE;
+    gtk_window_set_geometry_hints(GTK_WINDOW(mShell), nullptr,
+                                  &geometry, GdkWindowHints(hints));
+  }
+
+  nsBaseWidget::SetSizeConstraints(aConstraints);
+}
+
 NS_IMETHODIMP
 nsWindow::Show(bool aState)
 {
@@ -1002,6 +1019,8 @@ nsWindow::Show(bool aState)
 NS_IMETHODIMP
 nsWindow::Resize(PRInt32 aWidth, PRInt32 aHeight, bool aRepaint)
 {
+    ConstrainSize(&aWidth, &aHeight);
+
     // For top-level windows, aWidth and aHeight should possibly be
     // interpreted as frame bounds, but NativeResize treats these as window
     // bounds (Bug 581866).
@@ -1079,6 +1098,8 @@ NS_IMETHODIMP
 nsWindow::Resize(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight,
                        bool aRepaint)
 {
+    ConstrainSize(&aWidth, &aHeight);
+
     mBounds.x = aX;
     mBounds.y = aY;
     mBounds.SizeTo(GetSafeWindowSize(nsIntSize(aWidth, aHeight)));
diff --git a/widget/gtk2/nsWindow.h b/widget/gtk2/nsWindow.h
index da4e95eea5d..c0119b0255d 100644
--- a/widget/gtk2/nsWindow.h
+++ b/widget/gtk2/nsWindow.h
@@ -111,6 +111,7 @@ public:
     NS_IMETHOD         ConstrainPosition(bool aAllowSlop,
                                          PRInt32 *aX,
                                          PRInt32 *aY);
+    virtual void       SetSizeConstraints(const SizeConstraints& aConstraints);
     NS_IMETHOD         Move(PRInt32 aX,
                             PRInt32 aY);
     NS_IMETHOD         Show             (bool aState);
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index c3b42809379..e03aaca8746 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -163,7 +163,6 @@ enum nsTopLevelWidgetZPlacement { // for PlaceBehind()
   eZPlacementTop          // top of the window stack
 };
 
-
 /**
  * Preference for receiving IME updates
  *
@@ -351,6 +350,27 @@ struct InputContextAction {
   }
 };
 
+/**
+ * Size constraints for setting the minimum and maximum size of a widget.
+ * Values are in device pixels.
+ */
+struct SizeConstraints {
+  SizeConstraints()
+    : mMaxSize(NS_MAXSIZE, NS_MAXSIZE)
+  {
+  }
+
+  SizeConstraints(nsIntSize aMinSize,
+                  nsIntSize aMaxSize)
+  : mMinSize(aMinSize),
+    mMaxSize(aMaxSize)
+  {
+  }
+
+  nsIntSize mMinSize;
+  nsIntSize mMaxSize;
+};
+
 } // namespace widget
 } // namespace mozilla
 
@@ -369,6 +389,7 @@ class nsIWidget : public nsISupports {
     typedef mozilla::widget::IMEState IMEState;
     typedef mozilla::widget::InputContext InputContext;
     typedef mozilla::widget::InputContextAction InputContextAction;
+    typedef mozilla::widget::SizeConstraints SizeConstraints;
 
     // Used in UpdateThemeGeometries.
     struct ThemeGeometry {
@@ -658,7 +679,8 @@ class nsIWidget : public nsISupports {
     NS_IMETHOD MoveClient(PRInt32 aX, PRInt32 aY) = 0;
 
     /**
-     * Resize this widget. 
+     * Resize this widget. Any size constraints set for the window by a
+     * previous call to SetSizeConstraints will be applied.
      *
      * @param aWidth  the new width expressed in the parent's coordinate system
      * @param aHeight the new height expressed in the parent's coordinate system
@@ -670,7 +692,8 @@ class nsIWidget : public nsISupports {
                       bool     aRepaint) = 0;
 
     /**
-     * Move or resize this widget.
+     * Move or resize this widget. Any size constraints set for the window by
+     * a previous call to SetSizeConstraints will be applied.
      *
      * @param aX       the new x position expressed in the parent's coordinate system
      * @param aY       the new y position expressed in the parent's coordinate system
@@ -1588,6 +1611,26 @@ class nsIWidget : public nsISupports {
         return bounds;
     }
 
+    /**
+     * Set size constraints on the window size such that it is never less than
+     * the specified minimum size and never larger than the specified maximum
+     * size. The size constraints are sizes of the outer rectangle including
+     * the window frame and title bar. Use 0 for an unconstrained minimum size
+     * and NS_MAXSIZE for an unconstrained maximum size. Note that this method
+     * does not necessarily change the size of a window to conform to this size,
+     * thus Resize should be called afterwards.
+     *
+     * @param aConstraints: the size constraints in device pixels
+     */
+    virtual void SetSizeConstraints(const SizeConstraints& aConstraints) = 0;
+
+    /**
+     * Return the size constraints currently observed by the widget.
+     *
+     * @return the constraints in device pixels
+     */
+    virtual const SizeConstraints& GetSizeConstraints() const = 0;
+
 protected:
 
     // keep the list of children.  We also keep track of our siblings.
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 0417e29bc55..cd1cb5dfb25 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -1286,6 +1286,18 @@ BOOL CALLBACK nsWindow::UnregisterTouchForDescendants(HWND aWnd, LPARAM aMsg) {
  *
  **************************************************************/
 
+void
+nsWindow::SetSizeConstraints(const SizeConstraints& aConstraints)
+{
+  SizeConstraints c = aConstraints;
+  if (mWindowType != eWindowType_popup) {
+    c.mMinSize.width = NS_MAX(PRInt32(::GetSystemMetrics(SM_CXMINTRACK)), c.mMinSize.width);
+    c.mMinSize.height = NS_MAX(PRInt32(::GetSystemMetrics(SM_CYMINTRACK)), c.mMinSize.height);
+  }
+
+  nsBaseWidget::SetSizeConstraints(c);
+}
+
 // Move this component
 NS_METHOD nsWindow::Move(PRInt32 aX, PRInt32 aY)
 {
@@ -1356,6 +1368,7 @@ NS_METHOD nsWindow::Resize(PRInt32 aWidth, PRInt32 aHeight, bool aRepaint)
 {
   NS_ASSERTION((aWidth >=0 ) , "Negative width passed to nsWindow::Resize");
   NS_ASSERTION((aHeight >=0 ), "Negative height passed to nsWindow::Resize");
+  ConstrainSize(&aWidth, &aHeight);
 
   // Avoid unnecessary resizing calls
   if (mBounds.width == aWidth && mBounds.height == aHeight && !aRepaint)
@@ -1394,6 +1407,7 @@ NS_METHOD nsWindow::Resize(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeig
 {
   NS_ASSERTION((aWidth >=0 ),  "Negative width passed to nsWindow::Resize");
   NS_ASSERTION((aHeight >=0 ), "Negative height passed to nsWindow::Resize");
+  ConstrainSize(&aWidth, &aHeight);
 
   // Avoid unnecessary resizing calls
   if (mBounds.x == aX && mBounds.y == aY &&
@@ -2883,7 +2897,7 @@ nsIntPoint nsWindow::WidgetToScreenOffset()
 
 nsIntSize nsWindow::ClientToWindowSize(const nsIntSize& aClientSize)
 {
-  if (!IsPopupWithTitleBar())
+  if (mWindowType == eWindowType_popup && !IsPopupWithTitleBar())
     return aClientSize;
 
   // just use (200, 200) as the position
@@ -5063,6 +5077,22 @@ bool nsWindow::ProcessMessage(UINT msg, WPARAM &wParam, LPARAM &lParam,
     }
     break;
 
+    case WM_GETMINMAXINFO:
+    {
+      MINMAXINFO* mmi = (MINMAXINFO*)lParam;
+      // Set the constraints. The minimum size should also be constrained to the
+      // default window maximum size so that it fits on screen.
+      mmi->ptMinTrackSize.x =
+        NS_MIN((PRInt32)mmi->ptMaxTrackSize.x,
+               NS_MAX((PRInt32)mmi->ptMinTrackSize.x, mSizeConstraints.mMinSize.width));
+      mmi->ptMinTrackSize.y =
+        NS_MIN((PRInt32)mmi->ptMaxTrackSize.y,
+        NS_MAX((PRInt32)mmi->ptMinTrackSize.y, mSizeConstraints.mMinSize.height));
+      mmi->ptMaxTrackSize.x = NS_MIN((PRInt32)mmi->ptMaxTrackSize.x, mSizeConstraints.mMaxSize.width);
+      mmi->ptMaxTrackSize.y = NS_MIN((PRInt32)mmi->ptMaxTrackSize.y, mSizeConstraints.mMaxSize.height);
+    }
+    break;
+
     case WM_SETFOCUS:
       // If previous focused window isn't ours, it must have received the
       // redirected message.  So, we should forget it.
diff --git a/widget/windows/nsWindow.h b/widget/windows/nsWindow.h
index 83be8537d3d..5db78226954 100644
--- a/widget/windows/nsWindow.h
+++ b/widget/windows/nsWindow.h
@@ -94,6 +94,7 @@ public:
   NS_IMETHOD              Show(bool bState);
   virtual bool            IsVisible() const;
   NS_IMETHOD              ConstrainPosition(bool aAllowSlop, PRInt32 *aX, PRInt32 *aY);
+  virtual void            SetSizeConstraints(const SizeConstraints& aConstraints);
   NS_IMETHOD              Move(PRInt32 aX, PRInt32 aY);
   NS_IMETHOD              Resize(PRInt32 aWidth, PRInt32 aHeight, bool aRepaint);
   NS_IMETHOD              Resize(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight, bool aRepaint);
diff --git a/widget/xpwidgets/nsBaseWidget.cpp b/widget/xpwidgets/nsBaseWidget.cpp
index e2c6db93521..0038727b360 100644
--- a/widget/xpwidgets/nsBaseWidget.cpp
+++ b/widget/xpwidgets/nsBaseWidget.cpp
@@ -1323,6 +1323,18 @@ nsBaseWidget::GetGLFrameBufferFormat()
   return LOCAL_GL_NONE;
 }
 
+void nsBaseWidget::SetSizeConstraints(const SizeConstraints& aConstraints)
+{
+  mSizeConstraints = aConstraints;
+  // We can't ensure that the size is honored at this point because we're
+  // probably in the middle of a reflow.
+}
+
+const widget::SizeConstraints& nsBaseWidget::GetSizeConstraints() const
+{
+  return mSizeConstraints;
+}
+
 #ifdef DEBUG
 //////////////////////////////////////////////////////////////
 //
diff --git a/widget/xpwidgets/nsBaseWidget.h b/widget/xpwidgets/nsBaseWidget.h
index 8c17a3b0544..76c40a6f177 100644
--- a/widget/xpwidgets/nsBaseWidget.h
+++ b/widget/xpwidgets/nsBaseWidget.h
@@ -179,6 +179,9 @@ public:
 
   virtual PRUint32 GetGLFrameBufferFormat() MOZ_OVERRIDE;
 
+  virtual const SizeConstraints& GetSizeConstraints() const;
+  virtual void SetSizeConstraints(const SizeConstraints& aConstraints);
+
   /**
    * Use this when GetLayerManager() returns a BasicLayerManager
    * (nsBaseWidget::GetLayerManager() does). This sets up the widget's
@@ -283,6 +286,20 @@ protected:
     }
   }
 
+  /**
+   * Apply the current size constraints to the given size.
+   *
+   * @param aWidth width to constrain
+   * @param aHeight height to constrain
+   */
+  void ConstrainSize(PRInt32* aWidth, PRInt32* aHeight) const
+  {
+    *aWidth = NS_MAX(mSizeConstraints.mMinSize.width,
+                     NS_MIN(mSizeConstraints.mMaxSize.width, *aWidth));
+    *aHeight = NS_MAX(mSizeConstraints.mMinSize.height,
+                      NS_MIN(mSizeConstraints.mMaxSize.height, *aHeight));
+  }
+
 protected:
   /**
    * Starts the OMTC compositor destruction sequence.
@@ -322,6 +339,7 @@ protected:
   nsSizeMode        mSizeMode;
   nsPopupLevel      mPopupLevel;
   nsPopupType       mPopupType;
+  SizeConstraints   mSizeConstraints;
 
   // the last rolled up popup. Only set this when an nsAutoRollup is in scope,
   // so it can be cleared automatically.