Add non-member non-mutating methods for common gfx::Rect operations.

ui/gfx/rect_f.h

Index: ui/gfx/rect_f.h
diff --git a/ui/gfx/rect_f.h b/ui/gfx/rect_f.h
index 4ee1098bf9c14bc3e3196567170f45e6bbd97ad1..c527a7b0a2235e316f9911deea455683d9ad0d85 100644
--- a/ui/gfx/rect_f.h
+++ b/ui/gfx/rect_f.h
@@ -49,6 +49,34 @@ inline bool operator!=(const RectF& lhs, const RectF& rhs) {
   return !(lhs == rhs);
 }
 
+inline RectF Intersection(const RectF& a, const RectF& b) {
+  RectF result = a;
+  result.Intersect(b);
+  return result;
+}
+
+inline RectF Union(const RectF& a, const RectF& b) {
+  RectF result = a;
+  result.Union(b);
+  return result;
+}
+
+inline RectF Subtraction(const RectF& a, const RectF& b) {
+  RectF result = a;
+  result.Subtract(b);
+  return result;
+}
+
+inline RectF Scale(const RectF& r, float x_scale, float y_scale) {
+  RectF result = r;
+  result.Scale(x_scale, y_scale);
+  return result;
+}
+
+inline RectF Scale(const RectF& r, float scale) {
+  return Scale(r, scale, scale);
+}
+
 #if !defined(COMPILER_MSVC)
 extern template class RectBase<RectF, PointF, SizeF, InsetsF, float>;
 #endif