diff --git a/mozilla/widget/src/windows/nsWindow.cpp b/mozilla/widget/src/windows/nsWindow.cpp
index dbd158425c6..2a40dc98ef1 100644
--- a/mozilla/widget/src/windows/nsWindow.cpp
+++ b/mozilla/widget/src/windows/nsWindow.cpp
@@ -2127,6 +2127,22 @@ NS_METHOD nsWindow::Resize(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeig
     ResizeTranslucentWindow(aWidth, aHeight);
 #endif
 
+  // When resizing a borderless top-level window the window
+  // must be placed relative to its parent. WIN32 wants to
+  // place it relative to the screen, so we used the cached parent
+  // to calculate the parent's location then add the x,y passed to
+  // the resize to get the screen coordinate for the borderless top-level
+  // window.
+  if (mWindowType == eWindowType_popup) {
+    HWND parent = mBorderlessParent;
+    if (parent) {
+      RECT pr;
+      VERIFY(::GetWindowRect(parent, &pr));
+      aX += pr.left;
+      aY += pr.top;
+    }
+  }
+
   // Set cached value for lightweight and printing
   mBounds.x      = aX;
   mBounds.y      = aY;