Merge branch 'master' of github.com:mapbox/mapbox-gl-native into android-mason

Conflicts:
	Makefile
	platform/default/headless_view.cpp
	src/mbgl/map/map.cpp

include/mbgl/map/map.hpp

@@ -148,7 +148,14 @@ private:
     // Unconditionally performs a render with the current map state.
     void render();
 
-    bool async = false;
+    enum class Mode : uint8_t {
+        None, // we're not doing any processing
+        Continuous, // continually updating map
+        Static, // a once-off static image.
+    };
+
+    Mode mode = Mode::None;
+
     std::unique_ptr<uv::loop> loop;
     std::unique_ptr<uv::worker> workers;
     std::thread thread;