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diff --git a/dom/ipc/EffectsInfo.h b/dom/ipc/EffectsInfo.h
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+++ b/dom/ipc/EffectsInfo.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_EffectsInfo_h
+#define mozilla_dom_EffectsInfo_h
+
+#include "nsRect.h"
+
+namespace mozilla::dom {
+
+/**
+ * An EffectsInfo contains information for a remote browser about the graphical
+ * effects that are being applied to it by ancestor browsers in different
+ * processes.
+ */
+class EffectsInfo {
+ public:
+  EffectsInfo() { *this = EffectsInfo::FullyHidden(); }
+
+  static EffectsInfo VisibleWithinRect(
+      const nsRect& aVisibleRect, const Scale2D& aRasterScale,
+      const ParentLayerToScreenScale2D& aTransformToAncestorScale) {
+    return EffectsInfo{aVisibleRect, aRasterScale, aTransformToAncestorScale};
+  }
+  static EffectsInfo FullyHidden() {
+    return EffectsInfo{nsRect(), Scale2D(), ParentLayerToScreenScale2D()};
+  }
+
+  bool operator==(const EffectsInfo& aOther) const {
+    return mVisibleRect == aOther.mVisibleRect &&
+           mRasterScale == aOther.mRasterScale &&
+           mTransformToAncestorScale == aOther.mTransformToAncestorScale;
+  }
+  bool operator!=(const EffectsInfo& aOther) const {
+    return !(*this == aOther);
+  }
+
+  bool IsVisible() const { return !mVisibleRect.IsEmpty(); }
+
+  // The visible rect of this browser relative to the root frame. If this is
+  // empty then the browser can be considered invisible.
+  nsRect mVisibleRect;
+  // The desired scale factors to apply to rasterized content to match
+  // transforms applied in ancestor browsers. This gets propagated into the
+  // scale in StackingContextHelper.
+  Scale2D mRasterScale;
+  // TransformToAncestorScale to be set on FrameMetrics. It includes CSS
+  // transform scales and cumulative presshell resolution.
+  ParentLayerToScreenScale2D mTransformToAncestorScale;
+  // The difference between mScaleX/Y and mTransformToAncestorScale is the way
+  // that CSS transforms contribute to the scale. mTransformToAncestorScale
+  // includes the exact scale factors of the combined CSS transform whereas
+  // mScaleX/Y tries to take into account animating transform scales by picking
+  // a larger scale so that we don't have to re-rasterize every frame but rather
+  // we can just scale down  content rasterized on a previous frame.
+
+  // If you add new fields here, you must also update operator== and
+  // TabMessageUtils.
+
+ private:
+  EffectsInfo(const nsRect& aVisibleRect, const Scale2D& aRasterScale,
+              const ParentLayerToScreenScale2D& aTransformToAncestorScale)
+      : mVisibleRect(aVisibleRect),
+        mRasterScale(aRasterScale),
+        mTransformToAncestorScale(aTransformToAncestorScale) {}
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_EffectsInfo_h