Extract shell methods from ApplicationImpl into a base class, and pass this to Initialize() instead.

components/font_service/public/cpp/font_loader.h

Index: components/font_service/public/cpp/font_loader.h
diff --git a/components/font_service/public/cpp/font_loader.h b/components/font_service/public/cpp/font_loader.h
index b9fbd6fab9d78f5980215729b558bda0c1448f94..838b8ec701d621ba87c0ace82e4763d3bb71656f 100644
--- a/components/font_service/public/cpp/font_loader.h
+++ b/components/font_service/public/cpp/font_loader.h
@@ -18,13 +18,8 @@
 #include "third_party/skia/include/ports/SkFontConfigInterface.h"
 
 namespace mojo {
-class ApplicationImpl;
-namespace shell {
-namespace mojom {
 class Shell;
 }
-}
-}
 
 namespace font_service {
 namespace internal {
@@ -40,8 +35,7 @@ class FontServiceThread;
 class FontLoader : public SkFontConfigInterface,
                    public internal::MappedFontFile::Observer {
  public:
-  explicit FontLoader(mojo::shell::mojom::Shell* shell);
-  explicit FontLoader(mojo::ApplicationImpl* application_impl);
+  explicit FontLoader(mojo::Shell* shell);
   ~FontLoader() override;
 
   // Shuts down the background thread.