[range.view] Add complexity requirement normatively

Author: JohelEGP

source/ranges.tex

@@ -828,9 +828,7 @@
 
 \pnum
 The \tcode{View} concept specifies the requirements of a \libconcept{Range} type
-that has constant time copy, move, and assignment operators; that is, the cost of
-these operations is not proportional to the number of elements in the
-\tcode{View}.
+that has constant time copy, move, and assignment operators.
 
 \pnum
 \begin{example}
@@ -866,6 +864,11 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\tcode{T} models \libconcept{View} only if the execution time
+for the the initializations and assignments required by \libconcept{Copyable<T>}
+is not proportional to the number of elements in \tcode{T}.
+
 \pnum
 For a type \tcode{T}, the default value of \tcode{enable_view<T>} is:
 \begin{itemize}