[core] Modularize FileSource codebase (#15768)

* [core] Introduce FileSourceManager and use it for default platform impl

  - Add `FileSourceManager` interface that provides access to `FileSource`
    instances and means of registering / unregistering `FileSource` factories
  - Split `DefaultFileSource` into smaller parts
  - Add `DatabaseFileSource` interface and it's default implementation
  - Remove inter-dependencies between concrete `FileSource` classes

* [build] Add files to next build system

* [core] Add generic property setters / getters

* [core] Remove setOnlineStatus from OnlineFileSource interface

* [core] Hide threading implementation details from DatabaseFileSource interface

* [core] Make DB file source methods virtual

* [core] Add documentation for DatabaseFileSource and rename one method

* [core] Use simple callback instead of ActorRef

* [core] Remove ActorRef from OnlineFileSource public header

* [core] Add callback to FileSource::forward async API

* [core] Pass OfflineRegionDefinition by value

* [core] Update tests to use modular file sources

* [core] Update unit tests

* [core] Update unit tests after rebase

* [core] Backport low prio fix for cached requests

* [core] Backport pack database

* [core] Return removed factory from unRegisterFileSourceFactory

* [core] Rename shadowed args in onlinefilesource

* [core] Remove simple std::function callback aliases

* [core] Expose online file source property keys in public header file

* [test-runner] Add proxy file source test runner

* [cache] Update mbgl-cache utility to use new file source

* [metrics] Rebaseline binary size metrics

* [offline] Update offline utility

* [core] Update changelog

3 files changed, 14 insertions, 13 deletions

diff --git a/test/src/mbgl/test/fake_file_source.hpp b/test/src/mbgl/test/fake_file_source.hpp
index 8803e9576b..1faf4b7a18 100644
--- a/test/src/mbgl/test/fake_file_source.hpp
+++ b/test/src/mbgl/test/fake_file_source.hpp
@@ -2,6 +2,8 @@
 
 #include <mbgl/storage/file_source.hpp>
 #include <mbgl/storage/online_file_source.hpp>
+#include <mbgl/storage/resource.hpp>
+#include <mbgl/util/async_request.hpp>
 
 #include <algorithm>
 #include <list>
@@ -42,6 +44,8 @@ public:
         return std::make_unique<FakeFileRequest>(resource, callback, requests);
     }
 
+    bool canRequest(const Resource&) const override { return true; }
+
     bool respond(Resource::Kind kind, const Response& response) {
         auto it = std::find_if(requests.begin(), requests.end(), [&] (FakeFileRequest* fakeRequest) {
             return fakeRequest->resource.kind == kind;
@@ -60,7 +64,7 @@ public:
 
 };
 
-class FakeOnlineFileSource : public OnlineFileSource, public FakeFileSource {
+class FakeOnlineFileSource : public FakeFileSource {
 public:
     std::unique_ptr<AsyncRequest> request(const Resource& resource, Callback callback) override {
         return FakeFileSource::request(resource, callback);
@@ -69,7 +73,12 @@ public:
     bool respond(Resource::Kind kind, const Response& response) {
         return FakeFileSource::respond(kind, response);
     }
-};
 
+    mapbox::base::Value getProperty(const std::string& property) const override {
+        return onlineFs.getProperty(property);
+    }
+
+    OnlineFileSource onlineFs;
+};
 
 } // namespace mbgl
diff --git a/test/src/mbgl/test/stub_file_source.cpp b/test/src/mbgl/test/stub_file_source.cpp
index 0bbff84ff3..8870a45bdc 100644
--- a/test/src/mbgl/test/stub_file_source.cpp
+++ b/test/src/mbgl/test/stub_file_source.cpp
@@ -1,4 +1,5 @@
 #include <mbgl/test/stub_file_source.hpp>
+#include <mbgl/util/async_request.hpp>
 
 namespace mbgl {
 
diff --git a/test/src/mbgl/test/stub_file_source.hpp b/test/src/mbgl/test/stub_file_source.hpp
index 1135fa9a80..46bb33d5e2 100644
--- a/test/src/mbgl/test/stub_file_source.hpp
+++ b/test/src/mbgl/test/stub_file_source.hpp
@@ -2,6 +2,7 @@
 
 #include <mbgl/storage/file_source.hpp>
 #include <mbgl/storage/online_file_source.hpp>
+#include <mbgl/storage/resource.hpp>
 #include <mbgl/util/timer.hpp>
 
 #include <unordered_map>
@@ -19,6 +20,7 @@ public:
     ~StubFileSource() override;
 
     std::unique_ptr<AsyncRequest> request(const Resource&, Callback) override;
+    bool canRequest(const Resource&) const override { return true; }
     void remove(AsyncRequest*);
 
     using ResponseFunction = std::function<optional<Response> (const Resource&)>;
@@ -48,15 +50,4 @@ private:
     util::Timer timer;
 };
 
-class StubOnlineFileSource : public StubFileSource, public OnlineFileSource {
-public:
-
-    StubOnlineFileSource(ResponseType t = ResponseType::Asynchronous) : StubFileSource(t) {};
-    ~StubOnlineFileSource() override = default;
-
-    std::unique_ptr<AsyncRequest> request(const Resource& r, Callback c) override { return StubFileSource::request(r, c); };
-    void remove(AsyncRequest* r) { StubFileSource::remove(r); };
-};
-
-
 } // namespace mbgl