Restore rows() and cols() in aligned_array.h

These getters were removed in https://codereview.webrtc.org/1172163004
but are used in external code, so it makes sense to keep
them around to make the class more useful.

R=henrikg@webrtc.org, pkasting@chromium.org

Review URL: https://codereview.webrtc.org/1178043005.

Cr-Commit-Position: refs/heads/master@{#9478}

webrtc/system_wrappers/source/aligned_array_unittest.cc

@@ -51,5 +51,10 @@ TEST(AlignedArrayTest, CheckOverlap) {
   }
 }
 
-}  // namespace webrtc
+TEST(AlignedArrayTest, CheckRowsCols) {
+  AlignedArray<bool> arr(10, 7, 128);
+  ASSERT_EQ(arr.rows(), 10);
+  ASSERT_EQ(arr.cols(), 7);
+}
 
+}  // namespace webrtc