Move provider initialization-on-demand types to ContextProviders

Author: mcculls

components/context/src/main/java/datadog/context/ContextBinder.java

@@ -24,11 +24,4 @@ public interface ContextBinder {
   static void register(ContextBinder binder) {
     ContextProviders.customBinder = binder;
   }
-
-  final class Provided {
-    static final ContextBinder INSTANCE =
-        null != ContextProviders.customBinder
-            ? ContextProviders.customBinder
-            : new WeakMapContextBinder();
-  }
 }

components/context/src/main/java/datadog/context/ContextManager.java

@@ -31,11 +31,4 @@ public interface ContextManager {
   static void register(ContextManager manager) {
     ContextProviders.customManager = manager;
   }
-
-  final class Provided {
-    static final ContextManager INSTANCE =
-        null != ContextProviders.customManager
-            ? ContextProviders.customManager
-            : new ThreadLocalContextManager();
-  }
 }

components/context/src/main/java/datadog/context/ContextProviders.java

@@ -6,11 +6,25 @@ final class ContextProviders {
   static volatile ContextManager customManager;
   static volatile ContextBinder customBinder;
 
+  private static final class ProvidedManager {
+    static final ContextManager INSTANCE =
+        null != ContextProviders.customManager
+            ? ContextProviders.customManager
+            : new ThreadLocalContextManager();
+  }
+
+  private static final class ProvidedBinder {
+    static final ContextBinder INSTANCE =
+        null != ContextProviders.customBinder
+            ? ContextProviders.customBinder
+            : new WeakMapContextBinder();
+  }
+
   static ContextManager manager() {
-    return ContextManager.Provided.INSTANCE; // may be overridden by instrumentation
+    return ProvidedManager.INSTANCE; // may be overridden by instrumentation
   }
 
   static ContextBinder binder() {
-    return ContextBinder.Provided.INSTANCE; // may be overridden by instrumentation
+    return ProvidedBinder.INSTANCE; // may be overridden by instrumentation
   }
 }