[core] Fix performance-unnecessary-value-param errors in header files

As reported by clang-tidy-8.

include/mbgl/renderer/renderer_observer.hpp

@@ -34,7 +34,7 @@ public:
 
     // Style is missing an image
     using StyleImageMissingCallback = std::function<void()>;
-    virtual void onStyleImageMissing(const std::string&, StyleImageMissingCallback done) { done(); }
+    virtual void onStyleImageMissing(const std::string&, const StyleImageMissingCallback& done) { done(); }
     virtual void onRemoveUnusedStyleImages(const std::vector<std::string>&) {}
 };
 

include/mbgl/storage/file_source.hpp

@@ -48,6 +48,8 @@ public:
     // Allows to forward response from one source to another.
     // Optionally, callback can be provided to receive notification for forward
     // operation.
+    //
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     virtual void forward(const Resource&, const Response&, std::function<void()>) {}
 
     // When a file source supports consulting a local cache only, it must return true.
@@ -82,7 +84,7 @@ public:
     virtual mapbox::base::Value getProperty(const std::string&) const { return {}; };
 
     // When supported, sets the modifier of the requested resources.
-    virtual void setResourceTransform(ResourceTransform) {}
+    virtual void setResourceTransform(ResourceTransform) {} // NOLINT(performance-unnecessary-value-param)
 
 protected:
     FileSource() = default;

include/mbgl/storage/offline.hpp

@@ -191,7 +191,7 @@ public:
      * responsibility of the SDK bindings to wrap this object in an interface that
      * re-executes the user-provided implementation on the main thread.
      */
-    virtual void responseError(Response::Error) {}
+    virtual void responseError(Response::Error) {} // NOLINT(performance-unnecessary-value-param)
 
     /*
      * Implement this method to be notified when the limit on the number of Mapbox

platform/default/src/mbgl/map/map_snapshotter.cpp

@@ -39,8 +39,8 @@ public:
         delegate.invoke(&RendererObserver::onDidFinishRenderingFrame, mode, repaintNeeded, placementChanged);
     }
 
-    void onStyleImageMissing(const std::string& image, StyleImageMissingCallback cb) override {
-        delegate.invoke(&RendererObserver::onStyleImageMissing, image, std::move(cb));
+    void onStyleImageMissing(const std::string& image, const StyleImageMissingCallback& cb) override {
+        delegate.invoke(&RendererObserver::onStyleImageMissing, image, cb);
     }
 
 private:
@@ -76,7 +76,7 @@ public:
         rendererObserver->onDidFinishRenderingFrame(mode, repaintNeeded, placementChanged);
     }
 
-    void onStyleImageMissing(const std::string& id, StyleImageMissingCallback done) override {
+    void onStyleImageMissing(const std::string& id, const StyleImageMissingCallback& done) override {
         rendererObserver->onStyleImageMissing(id, done);
     }
 

src/mbgl/map/map_impl.cpp

@@ -167,7 +167,7 @@ void Map::Impl::jumpTo(const CameraOptions& camera) {
     onUpdate();
 }
 
-void Map::Impl::onStyleImageMissing(const std::string& id, std::function<void()> done) {
+void Map::Impl::onStyleImageMissing(const std::string& id, const std::function<void()>& done) {
     if (!style->getImage(id)) observer.onStyleImageMissing(id);
 
     done();

src/mbgl/map/map_impl.hpp

@@ -45,7 +45,7 @@ public:
     void onDidFinishRenderingFrame(RenderMode, bool, bool) final;
     void onWillStartRenderingMap() final;
     void onDidFinishRenderingMap() final;
-    void onStyleImageMissing(const std::string&, std::function<void()>) final;
+    void onStyleImageMissing(const std::string&, const std::function<void()>&) final;
     void onRemoveUnusedStyleImages(const std::vector<std::string>&) final;
 
     // Map

src/mbgl/renderer/image_manager_observer.hpp

@@ -8,7 +8,7 @@ class ImageManagerObserver {
 public:
     virtual ~ImageManagerObserver() = default;
 
-    virtual void onStyleImageMissing(const std::string&, std::function<void()> done) { done(); }
+    virtual void onStyleImageMissing(const std::string&, const std::function<void()>& done) { done(); }
     virtual void onRemoveUnusedStyleImages(const std::vector<std::string>&) {}
 };
 

src/mbgl/renderer/render_orchestrator.cpp

@@ -727,8 +727,8 @@ void RenderOrchestrator::onTileChanged(RenderSource&, const OverscaledTileID&) {
     observer->onInvalidate();
 }
 
-void RenderOrchestrator::onStyleImageMissing(const std::string& id, std::function<void()> done) {
-    observer->onStyleImageMissing(id, std::move(done));
+void RenderOrchestrator::onStyleImageMissing(const std::string& id, const std::function<void()>& done) {
+    observer->onStyleImageMissing(id, done);
 }
 
 void RenderOrchestrator::onRemoveUnusedStyleImages(const std::vector<std::string>& unusedImageIDs) {

src/mbgl/renderer/render_orchestrator.hpp

@@ -100,7 +100,7 @@ private:
     void onTileError(RenderSource&, const OverscaledTileID&, std::exception_ptr) override;
 
     // ImageManagerObserver implementation
-    void onStyleImageMissing(const std::string&, std::function<void()>) override;
+    void onStyleImageMissing(const std::string&, const std::function<void()>&) override;
     void onRemoveUnusedStyleImages(const std::vector<std::string>&) override;
 
     RendererObserver* observer;

src/mbgl/sprite/sprite_loader_observer.hpp

@@ -15,7 +15,10 @@ class Image;
 class SpriteLoaderObserver {
 public:
     virtual ~SpriteLoaderObserver() = default;
+
+    // NOLINTNEXTLINE(performance-unnecessary-value-param)
     virtual void onSpriteLoaded(std::vector<Immutable<style::Image::Impl>>) {}
+
     virtual void onSpriteError(std::exception_ptr) {}
 };
 

test/renderer/image_manager.test.cpp

@@ -140,7 +140,7 @@ class StubImageManagerObserver : public ImageManagerObserver {
     public:
     int count = 0;
     std::function<void (const std::string&)> imageMissing = [](const std::string&){};
-    void onStyleImageMissing(const std::string& id, std::function<void()> done) override {
+    void onStyleImageMissing(const std::string& id, const std::function<void()>& done) override {
         count++;
         imageMissing(id);
         done();