[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, 2 insertions, 4 deletions

diff --git a/test/api/api_misuse.test.cpp b/test/api/api_misuse.test.cpp
index 8899173071..9490c14e1f 100644
--- a/test/api/api_misuse.test.cpp
+++ b/test/api/api_misuse.test.cpp
@@ -7,7 +7,6 @@
 #include <mbgl/renderer/backend_scope.hpp>
 #include <mbgl/gl/headless_frontend.hpp>
 #include <mbgl/storage/online_file_source.hpp>
-#include <mbgl/util/default_thread_pool.hpp>
 #include <mbgl/util/exception.hpp>
 #include <mbgl/util/run_loop.hpp>
 
@@ -23,12 +22,11 @@ TEST(API, RenderWithoutCallback) {
     util::RunLoop loop;
 
     StubFileSource fileSource;
-    ThreadPool threadPool(4);
     float pixelRatio { 1 };
-    HeadlessFrontend frontend { pixelRatio, fileSource, threadPool };
+    HeadlessFrontend frontend { pixelRatio, fileSource };
 
     auto map = std::make_unique<Map>(frontend, MapObserver::nullObserver(), frontend.getSize(),
-                                     pixelRatio, fileSource, threadPool,
+                                     pixelRatio, fileSource,
                                      MapOptions().withMapMode(MapMode::Static));
     map->renderStill(nullptr);