[core] Fix modernize-return-braced-init-list errors in header files

As reported by clang-tidy-8.

include/mbgl/util/char_array_buffer.hpp

@@ -43,7 +43,7 @@ private:
         if (dir == std::ios_base::beg) current_ = std::min(begin_ + off, end_);
         else if (dir == std::ios_base::cur) current_ = std::min(current_ + off, end_);
         else current_ = std::max(end_ - off, begin_); // dir == std::ios_base::end
-        return pos_type(off_type(current_ - begin_));
+        return {off_type(current_ - begin_)};
     }
 
     char const * const begin_;

include/mbgl/util/geo.hpp

@@ -82,14 +82,10 @@ public:
 class LatLngBounds {
 public:
     // Return a bounds covering the entire (unwrapped) world.
-    static LatLngBounds world() {
-        return LatLngBounds({-90, -180}, {90, 180});
-    }
+    static LatLngBounds world() { return {{-90, -180}, {90, 180}}; }
 
     // Return the bounds consisting of the single point.
-    static LatLngBounds singleton(const LatLng& a) {
-        return LatLngBounds(a, a);
-    }
+    static LatLngBounds singleton(const LatLng& a) { return {a, a}; }
 
     // Return the convex hull of two points; the smallest bounds that contains both.
     static LatLngBounds hull(const LatLng& a, const LatLng& b) {
@@ -126,13 +122,10 @@ public:
 
     LatLng southwest() const { return sw; }
     LatLng northeast() const { return ne; }
-    LatLng southeast() const { return LatLng(south(), east()); }
-    LatLng northwest() const { return LatLng(north(), west()); }
+    LatLng southeast() const { return {south(), east()}; }
+    LatLng northwest() const { return {north(), west()}; }
 
-    LatLng center() const {
-        return LatLng((sw.latitude() + ne.latitude()) / 2,
-                      (sw.longitude() + ne.longitude()) / 2);
-    }
+    LatLng center() const { return {(sw.latitude() + ne.latitude()) / 2, (sw.longitude() + ne.longitude()) / 2}; }
 
     LatLng constrain(const LatLng& p) const;
 

include/mbgl/util/projection.hpp

@@ -61,7 +61,7 @@ public:
         const double easting  = util::EARTH_RADIUS_M * constrainedLongitude * util::DEG2RAD;
         const double northing = 0.5 * util::EARTH_RADIUS_M * std::log((1 + f) / (1 - f));
 
-        return ProjectedMeters(northing, easting);
+        return {northing, easting};
     }
 
     static LatLng latLngForProjectedMeters(const ProjectedMeters& projectedMeters) {
@@ -71,7 +71,7 @@ public:
         latitude = util::clamp(latitude, -util::LATITUDE_MAX, util::LATITUDE_MAX);
         longitude = util::clamp(longitude, -util::LONGITUDE_MAX, util::LONGITUDE_MAX);
 
-        return LatLng(latitude, longitude);
+        return {latitude, longitude};
     }
 
     static Point<double> project(const LatLng& latLng, double scale) {

src/mbgl/annotation/symbol_annotation_impl.hpp

@@ -72,7 +72,7 @@ struct indexable<std::shared_ptr<const mbgl::SymbolAnnotationImpl>> {
     using result_type = mbgl::LatLng;
     mbgl::LatLng operator()(const std::shared_ptr<const mbgl::SymbolAnnotationImpl>& v) const {
         const mbgl::Point<double>& p = v->annotation.geometry;
-        return mbgl::LatLng(p.y, p.x);
+        return {p.y, p.x};
     }
 };
 

src/mbgl/style/rapidjson_conversion.hpp

@@ -35,7 +35,7 @@ public:
 
     static optional<const JSValue*> objectMember(const JSValue* value, const char * name) {
         if (!value->HasMember(name)) {
-            return optional<const JSValue*>();
+            return {};
         }
         const JSValue* const& member = &(*value)[name];
         return {member};

src/mbgl/util/tile_range.hpp

@@ -29,7 +29,7 @@ public:
         const auto minY = static_cast<uint32_t>(util::clamp(std::floor(neProj.y), 0.0 , maxTile));
         const auto maxY = static_cast<uint32_t>(util::clamp(std::floor(swProj.y), 0.0, maxTile));
 
-        return TileRange({ {minX, minY}, {maxX, maxY} }, {minZoom, maxZoom});
+        return {{{minX, minY}, {maxX, maxY}}, {minZoom, maxZoom}};
     }
 
     // Compute the range of tiles covered by the bounds.