[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`.

3 files changed, 5 insertions, 15 deletions

diff --git a/test/style/source.test.cpp b/test/style/source.test.cpp
index f0ff1f81b4..289e41c75f 100644
--- a/test/style/source.test.cpp
+++ b/test/style/source.test.cpp
@@ -31,7 +31,6 @@
 #include <mbgl/util/image.hpp>
 
 #include <mbgl/util/tileset.hpp>
-#include <mbgl/util/shared_thread_pool.hpp>
 #include <mbgl/util/logging.hpp>
 #include <mbgl/util/optional.hpp>
 #include <mbgl/util/range.hpp>
@@ -55,8 +54,7 @@ public:
     StubRenderSourceObserver renderSourceObserver;
     Transform transform;
     TransformState transformState;
-    ThreadPool threadPool { 1 };
-    Style style { loop, fileSource, 1 };
+    Style style { fileSource, 1 };
     AnnotationManager annotationManager { style };
     ImageManager imageManager;
     GlyphManager glyphManager { fileSource };
@@ -65,7 +63,6 @@ public:
         1.0,
         MapDebugOptions(),
         transformState,
-        threadPool,
         fileSource,
         MapMode::Continuous,
         annotationManager,
@@ -763,7 +760,6 @@ TEST(Source, ImageSourceImageUpdate) {
 
 TEST(Source, CustomGeometrySourceSetTileData) {
     SourceTest test;
-    std::shared_ptr<ThreadPool> threadPool = sharedThreadPool();
     CustomGeometrySource source("source", CustomGeometrySource::Options());
     source.loadDescription(test.fileSource);
 
diff --git a/test/style/style.test.cpp b/test/style/style.test.cpp
index 7f57651331..72f74d3b01 100644
--- a/test/style/style.test.cpp
+++ b/test/style/style.test.cpp
@@ -9,7 +9,6 @@
 #include <mbgl/style/layers/line_layer.hpp>
 #include <mbgl/util/io.hpp>
 #include <mbgl/util/run_loop.hpp>
-#include <mbgl/util/default_thread_pool.hpp>
 
 #include <memory>
 
@@ -19,9 +18,8 @@ using namespace mbgl::style;
 TEST(Style, Properties) {
     util::RunLoop loop;
 
-    ThreadPool threadPool{ 1 };
     StubFileSource fileSource;
-    Style::Impl style { threadPool, fileSource, 1.0 };
+    Style::Impl style { fileSource, 1.0 };
 
     style.loadJSON(R"STYLE({"name": "Test"})STYLE");
     ASSERT_EQ("Test", style.getName());
@@ -62,9 +60,8 @@ TEST(Style, Properties) {
 TEST(Style, DuplicateSource) {
     util::RunLoop loop;
 
-    ThreadPool threadPool{ 1 };
     StubFileSource fileSource;
-    Style::Impl style { threadPool, fileSource, 1.0 };
+    Style::Impl style { fileSource, 1.0 };
 
     style.loadJSON(util::read_file("test/fixtures/resources/style-unused-sources.json"));
 
@@ -84,9 +81,8 @@ TEST(Style, RemoveSourceInUse) {
     auto log = new FixtureLogObserver();
     Log::setObserver(std::unique_ptr<Log::Observer>(log));
 
-    ThreadPool threadPool{ 1 };
     StubFileSource fileSource;
-    Style::Impl style { threadPool, fileSource, 1.0 };
+    Style::Impl style { fileSource, 1.0 };
 
     style.loadJSON(util::read_file("test/fixtures/resources/style-unused-sources.json"));
 
diff --git a/test/style/style_layer.test.cpp b/test/style/style_layer.test.cpp
index 7598d888e9..d6a926c631 100644
--- a/test/style/style_layer.test.cpp
+++ b/test/style/style_layer.test.cpp
@@ -21,7 +21,6 @@
 #include <mbgl/test/stub_file_source.hpp>
 #include <mbgl/util/color.hpp>
 #include <mbgl/util/run_loop.hpp>
-#include <mbgl/util/default_thread_pool.hpp>
 #include <mbgl/util/io.hpp>
 
 #include <memory>
@@ -283,9 +282,8 @@ TEST(Layer, DuplicateLayer) {
     util::RunLoop loop;
 
     // Setup style
-    ThreadPool threadPool{ 1 };
     StubFileSource fileSource;
-    Style::Impl style { threadPool, fileSource, 1.0 };
+    Style::Impl style { fileSource, 1.0 };
     style.loadJSON(util::read_file("test/fixtures/resources/style-unused-sources.json"));
 
     // Add initial layer