Rewrite the preprocessor infrastructure to return events as part of the result.

--
MOS_MIGRATED_REVID=102658808
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/PackageFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/PackageFunction.java
index 9e3b8d5..5cb7685 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/PackageFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/PackageFunction.java
@@ -797,12 +797,10 @@
       try {
         Globber globber = packageFactory.createLegacyGlobber(buildFilePath.getParentDirectory(),
             packageId, packageLocator);
-        StoredEventHandler localReporter = new StoredEventHandler();
         Preprocessor.Result preprocessingResult = preprocessCache.getIfPresent(packageId);
         if (preprocessingResult == null) {
           preprocessingResult = replacementSource == null
-              ? packageFactory.preprocess(packageId, buildFilePath, inputSource, globber,
-                  localReporter)
+              ? packageFactory.preprocess(packageId, buildFilePath, inputSource, globber)
               : Preprocessor.Result.noPreprocessing(replacementSource);
           preprocessCache.put(packageId, preprocessingResult);
         }
@@ -821,7 +819,7 @@
         preprocessCache.invalidate(packageId);
 
         pkgBuilder = packageFactory.createPackageFromPreprocessingResult(externalPkg, packageId,
-            buildFilePath, preprocessingResult, localReporter.getEvents(), preludeStatements,
+            buildFilePath, preprocessingResult, preprocessingResult.events, preludeStatements,
             importResult.importMap, importResult.fileDependencies, packageLocator,
             defaultVisibility, globber);
         numPackagesLoaded.incrementAndGet();