One last bit of base::size cleanup.

BUG=837308

Change-Id: I7ff4ac0d0d6399daac1f934a85924e0817017680
Reviewed-on: https://chromium-review.googlesource.com/c/1404703
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621594}

components/sync/base/unique_position_unittest.cc

@@ -7,7 +7,6 @@
 #include <algorithm>
 #include <functional>
 #include <memory>
-#include <type_traits>
 #include <vector>
 
 #include "base/base64.h"
@@ -216,7 +215,7 @@ TEST_F(RelativePositioningTest, ComparisonSanityTest2) {
 // Exercise comparision functions by sorting and re-sorting the list.
 TEST_F(RelativePositioningTest, SortPositions) {
   ASSERT_EQ(kNumPositions, kNumSortedPositions);
-  UniquePosition positions[std::extent<decltype(kPositionArray)>()];
+  UniquePosition positions[base::size(kPositionArray)];
   for (size_t i = 0; i < kNumPositions; ++i) {
     positions[i] = kPositionArray[i];
   }
@@ -232,7 +231,7 @@ TEST_F(RelativePositioningTest, SortPositions) {
 // Some more exercise for the comparison function.
 TEST_F(RelativePositioningTest, ReverseSortPositions) {
   ASSERT_EQ(kNumPositions, kNumSortedPositions);
-  UniquePosition positions[std::extent<decltype(kPositionArray)>()];
+  UniquePosition positions[base::size(kPositionArray)];
   for (size_t i = 0; i < kNumPositions; ++i) {
     positions[i] = kPositionArray[i];
   }