Make one arg ctors explicit

platform/default/asset_request_zip.cpp

@@ -17,7 +17,7 @@ namespace mbgl {
 
 class AssetZipContext : public AssetContext {
 public:
-    AssetZipContext(uv_loop_t *loop);
+    explicit AssetZipContext(uv_loop_t *loop);
     ~AssetZipContext();
 
     RequestBase* createRequest(const Resource& resource,

platform/default/http_request_curl.cpp

@@ -60,7 +60,7 @@ class HTTPCURLContext : public HTTPContext {
     MBGL_STORE_THREAD(tid)
 
 public:
-    HTTPCURLContext(uv_loop_t *loop);
+    explicit HTTPCURLContext(uv_loop_t *loop);
     ~HTTPCURLContext();
 
     RequestBase* createRequest(const Resource&,

platform/default/sqlite_cache_impl.hpp

@@ -14,7 +14,7 @@ namespace mbgl {
 
 class SQLiteCache::Impl {
 public:
-    Impl(const std::string &path = ":memory:");
+    explicit Impl(const std::string &path = ":memory:");
     ~Impl();
 
     void get(const Resource&, Callback);

src/mbgl/map/tile_worker.cpp

@@ -73,7 +73,7 @@ void TileWorker::redoPlacement(float angle, bool collisionDebug) {
 template <typename T>
 struct PropertyEvaluator {
     typedef T result_type;
-    PropertyEvaluator(float z_) : z(z_) {}
+    explicit PropertyEvaluator(float z_) : z(z_) {}
 
     template <typename P, typename std::enable_if<std::is_convertible<P, T>::value, int>::type = 0>
     T operator()(const P &value) const {

src/mbgl/util/worker.cpp

@@ -14,7 +14,7 @@ namespace mbgl {
 
 class Worker::Impl {
 public:
-    Impl(FileSource* fs) {
+    explicit Impl(FileSource* fs) {
         // FIXME: Workers should not access the FileSource but it
         // is currently needed because of GlyphsPBF. See #1664.
         util::ThreadContext::setFileSource(fs);

src/mbgl/util/worker.hpp

@@ -16,7 +16,7 @@ class LiveTile;
 
 class Worker : public mbgl::util::noncopyable {
 public:
-    Worker(std::size_t count);
+    explicit Worker(std::size_t count);
     ~Worker();
 
     // Request work be done on a thread pool. Callbacks are executed on the invoking