Canvas objects did not mark themselves for layout when they're a flex item

third_party/WebKit/Source/core/layout/LayoutHTMLCanvas.cpp

Index: third_party/WebKit/Source/core/layout/LayoutHTMLCanvas.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutHTMLCanvas.cpp b/third_party/WebKit/Source/core/layout/LayoutHTMLCanvas.cpp
index cd52e66b8a434a7d42469e8b5fc7a64da3d4b0e8..ce9b4d10f4cbb32a1d7af6c7e5b31699ddd50790 100644
--- a/third_party/WebKit/Source/core/layout/LayoutHTMLCanvas.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutHTMLCanvas.cpp
@@ -71,8 +71,13 @@ void LayoutHTMLCanvas::canvasSizeChanged()
     LayoutSize oldSize = size();
     updateLogicalWidth();
     updateLogicalHeight();
-    if (oldSize == size())
+    if (oldSize == size() && !hasOverrideLogicalContentWidth() && !hasOverrideLogicalContentHeight()) {
+        // If we have an override size, then we're probably a flex item, and the
+        // check above is insufficient because updateLogical{Width,Height} just
+        // used the override size. We actually have to mark ourselves as needing
+        // layout so the flex algorithm can run and compute our size correctly.
         return;
+    }
 
     if (!selfNeedsLayout())
         setNeedsLayout(LayoutInvalidationReason::SizeChanged);