[core] Inline TileSource::isRequired, remove unused isOptional

src/mbgl/tile/tile_source.hpp

@@ -44,14 +44,6 @@ class TileSource : private util::noncopyable {
  }
 
 private:
- bool isOptional() const {
- return necessity == Necessity::Optional;
- }
-
- bool isRequired() const {
- return necessity == Necessity::Required;
- }
-
  // called when the tile is one of the ideal tiles that we want to show definitely. the tile source
  // should try to make every effort (e.g. fetch from internet, or revalidate existing resources).
  void makeRequired();

src/mbgl/tile/tile_source_impl.hpp

@@ -34,7 +34,7 @@ TileSource<T>::TileSource(T& tileData_,
  } else {
  // When the FileSource doesn't support optional requests, we do nothing until the
  // data is definitely required.
- if (isRequired()) {
+ if (necessity == Necessity::Required) {
  loadRequired();
  } else {
  // We're using this field to check whether the pending request is optional or required.
@@ -62,7 +62,7 @@ void TileSource<T>::loadOptional() {
  loadedData(res);
  }
 
- if (isRequired()) {
+ if (necessity == Necessity::Required) {
  loadRequired();
  }
  });