[core] Make the BackgroundScheduler a singleton

- Do not carry it over everywhere as parameter, it is a shared
  instance anyway and the lifecycle is pretty much the app lifecycle
  from the moment we instantiate a map.
- Rename to BackgroundScheduler because it is a Scheduler that will
  do tasks in the background, we don't make assumptions if it is a
  thread pool or a single thread.
- Most importantly, remove the dependency from `core` on `platform`.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/mbgl/sprite/sprite_loader.hpp b/src/mbgl/sprite/sprite_loader.hpp
index 0daf46be9c..0b7d37fa14 100644
--- a/src/mbgl/sprite/sprite_loader.hpp
+++ b/src/mbgl/sprite/sprite_loader.hpp
@@ -12,7 +12,6 @@
 
 namespace mbgl {
 
-class Scheduler;
 class FileSource;
 class SpriteLoaderObserver;
 
@@ -21,7 +20,7 @@ public:
     SpriteLoader(float pixelRatio);
     ~SpriteLoader();
 
-    void load(const std::string& url, Scheduler&, FileSource&);
+    void load(const std::string& url, FileSource&);
 
     void setObserver(SpriteLoaderObserver*);