Synchronize access to the AidlLanguage constructor and registration

Fixes: 280346978
Test: N/A
Change-Id: I781fe8943492b6c71a4ab9958952287d2385c2b4

Author: alanv

lint-checks/src/main/java/androidx/com/android/tools/idea/lang/aidl/AidlLanguage.java

@@ -22,14 +22,20 @@
  * Android IDL Language.
  */
 public class AidlLanguage extends Language {
+  private static final Object INSTANCE_LOCK = new Object();
+
   public static final Language INSTANCE = getOrCreate();
 
   private static Language getOrCreate() {
-    Language lang = Language.findLanguageByID(ID);
-    if (lang != null) {
-      return lang;
+    // The Language class is not thread-safe, so this is a best-effort to avoid a race condition
+    // during our own access across multiple lint worker threads.
+    synchronized (INSTANCE_LOCK) {
+      Language lang = Language.findLanguageByID(ID);
+      if (lang != null) {
+        return lang;
+      }
+      return new AidlLanguage();
     }
-    return new AidlLanguage();
   }
 
   @NonNls private static final String ID = "AIDL";