--- a/layout/generic/nsVideoFrame.cpp
+++ b/layout/generic/nsVideoFrame.cpp
@@ -372,17 +372,19 @@ nsVideoFrame::Reflow(nsPresContext* aPre
                                        aReflowInput,
                                        child,
                                        availableSize);
       ReflowOutput kidDesiredSize(kidReflowInput);
       ReflowChild(child, aPresContext, kidDesiredSize, kidReflowInput,
                   borderPadding.left, borderPadding.top, 0, aStatus);
 
       if (child->GetContent() == mVideoControls && isBSizeShrinkWrapping) {
-        contentBoxBSize = kidDesiredSize.BSize(myWM);
+        // Resolve our own BSize based on the controls' size in the same axis.
+        contentBoxBSize = myWM.IsOrthogonalTo(wm) ?
+          kidDesiredSize.ISize(wm) : kidDesiredSize.BSize(wm);
       }
 
       FinishReflowChild(child, aPresContext,
                         kidDesiredSize, &kidReflowInput,
                         borderPadding.left, borderPadding.top, 0);
     }
 
     if (child->GetContent() == mVideoControls && child->GetSize() != oldChildSize) {