lock the StyleBucket to avoid crashing

stopgap until we have a solution that doesn't mutate the style objects while parsing a tile

src/mbgl/map/tile_parser.cpp

@@ -126,12 +126,14 @@ void TileParser::applyLayoutProperty(PropertyKey key, ClassProperties &classProp
 
 template <>
 void TileParser::applyLayoutProperties<FillProperties>(StyleBucket &bucket_desc, const float) {
+    auto lock = bucket_desc.lock();
     bucket_desc.render.set<StyleBucketFill>();
     // no-op; Fill buckets don't currently have any applicable layout properties
 }
 
 template<>
 void TileParser::applyLayoutProperties<LineProperties>(StyleBucket &bucket_desc, const float z) {
+    auto lock = bucket_desc.lock();
     bucket_desc.render.set<StyleBucketLine>();
     StyleBucketLine &line = bucket_desc.render.get<StyleBucketLine>();
     applyLayoutProperty(PropertyKey::LineCap, bucket_desc.layout, line.cap, z);
@@ -142,6 +144,7 @@ void TileParser::applyLayoutProperties<LineProperties>(StyleBucket &bucket_desc,
 
 template<>
 void TileParser::applyLayoutProperties<SymbolProperties>(StyleBucket &bucket_desc, const float z) {
+    auto lock = bucket_desc.lock();
     bucket_desc.render.set<StyleBucketSymbol>();
     StyleBucketSymbol &symbol = bucket_desc.render.get<StyleBucketSymbol>();
     applyLayoutProperty(PropertyKey::SymbolPlacement, bucket_desc.layout, symbol.placement, z);

src/mbgl/style/style_bucket.cpp

@@ -1,4 +1,6 @@
 #include <mbgl/style/style_bucket.hpp>
+#include <mbgl/util/std.hpp>
+#include <mbgl/util/uv_detail.hpp>
 
 namespace mbgl {
 
@@ -8,7 +10,7 @@ template<> const StyleBucketSymbol &defaultLayoutProperties() { static StyleBuck
 template<> const StyleBucketRaster &defaultLayoutProperties() { static StyleBucketRaster p; return p; }
 template<> const StyleBucketBackground &defaultLayoutProperties() { static StyleBucketBackground p; return p; }
 
-StyleBucket::StyleBucket(StyleLayerType type_) : type(type_) {
+StyleBucket::StyleBucket(StyleLayerType type_) : type(type_), mtx(util::make_unique<uv::mutex>()) {
     switch (type) {
         case StyleLayerType::Fill: render.set<StyleBucketFill>(); break;
         case StyleLayerType::Line: render.set<StyleBucketLine>(); break;
@@ -18,4 +20,8 @@ StyleBucket::StyleBucket(StyleLayerType type_) : type(type_) {
     }
 }
 
+uv::lock StyleBucket::lock() {
+    return uv::lock(mtx);
+}
+
 }

src/mbgl/style/style_bucket.hpp

@@ -9,6 +9,7 @@
 #include <mbgl/util/variant.hpp>
 #include <mbgl/util/noncopyable.hpp>
 #include <mbgl/util/ptr.hpp>
+#include <mbgl/util/uv.hpp>
 #include <mbgl/style/class_properties.hpp>
 
 #include <forward_list>
@@ -123,6 +124,12 @@ class StyleBucket : public util::noncopyable {
     float min_zoom = -std::numeric_limits<float>::infinity();
     float max_zoom = std::numeric_limits<float>::infinity();
     VisibilityType visibility = VisibilityType::Visible;
+
+public:
+    uv::lock lock();
+
+private:
+    std::unique_ptr<uv::mutex> mtx;
 };
 
 template <typename T>

src/mbgl/style/style_parser.cpp

@@ -3,6 +3,7 @@
 #include <mbgl/style/style_layer_group.hpp>
 #include <mbgl/util/constants.hpp>
 #include <mbgl/util/std.hpp>
+#include <mbgl/util/uv_detail.hpp>
 #include <mbgl/platform/log.hpp>
 #include <csscolorparser/csscolorparser.hpp>
 
@@ -318,7 +319,6 @@ template <> inline float defaultBaseValue<Color>() { return 1.0; }
 
 template <typename T>
 std::tuple<bool, Function<T>> StyleParser::parseFunction(JSVal value, const char *property_name) {
-
     if (!value.IsObject()) {
         return std::tuple<bool, Function<T>> { true, ConstantFunction<T>(std::get<1>(parseProperty<T>(value, property_name))) };
     }