Remove 'Filename' parameter from BeginSourceFileAction.

No-one was using this, and it's not meaningful in general -- FrontendActions
can be run on inputs that don't have a corresponding source file. The current
frontend input can be obtained by asking the FrontendAction if any future
action actually needs it.

llvm-svn: 305045
diff --git a/clang/unittests/Frontend/FrontendActionTest.cpp b/clang/unittests/Frontend/FrontendActionTest.cpp
index 68181c7..ce01445 100644
--- a/clang/unittests/Frontend/FrontendActionTest.cpp
+++ b/clang/unittests/Frontend/FrontendActionTest.cpp
@@ -37,12 +37,11 @@
   bool ActOnEndOfTranslationUnit;
   std::vector<std::string> decl_names;
 
-  bool BeginSourceFileAction(CompilerInstance &ci,
-                             StringRef filename) override {
+  bool BeginSourceFileAction(CompilerInstance &ci) override {
     if (EnableIncrementalProcessing)
       ci.getPreprocessor().enableIncrementalProcessing();
 
-    return ASTFrontendAction::BeginSourceFileAction(ci, filename);
+    return ASTFrontendAction::BeginSourceFileAction(ci);
   }
 
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,