Revert "Workaround FD leaks from clang module files in performSema"

This reverts commit r25038.

Swift SVN r25041

lib/Frontend/Frontend.cpp

@@ -26,8 +26,6 @@
 #include "swift/Parse/Lexer.h"
 #include "swift/SIL/SILModule.h"
 #include "swift/Serialization/SerializedModuleLoader.h"
-#include "clang/Lex/HeaderSearch.h"
-#include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/CommandLine.h"
@@ -223,22 +221,6 @@ Module *CompilerInstance::getMainModule() {
   return MainModule;
 }
 
-namespace {
-class CloseClangModuleFiles {
-  clang::Preprocessor &PP;
-public:
-  CloseClangModuleFiles(clang::Preprocessor &PP) : PP(PP) {}
-  ~CloseClangModuleFiles() {
-    clang::ModuleMap &ModMap = PP.getHeaderSearchInfo().getModuleMap();
-    for (auto I = ModMap.module_begin(), E = ModMap.module_end(); I != E; ++I) {
-      clang::Module *M = I->second;
-      if (!M->isSubModule() && M->getASTFile())
-        M->getASTFile()->closeFile();
-    }
-  }
-};
-} // end anonymous namespace
-
 void CompilerInstance::performSema() {
   const FrontendOptions &options = Invocation.getFrontendOptions();
   const SourceFileKind Kind = Invocation.getInputKind();
@@ -272,11 +254,6 @@ void CompilerInstance::performSema() {
   auto clangImporter =
     static_cast<ClangImporter *>(Context->getClangModuleLoader());
 
-  // When we exit, we won't build any more clang modules, so close the .pcm
-  // files to prevent fd leaks in clients that cache the AST.
-  // FIXME: Remove this once rdar://problem/19720334 is complete.
-  CloseClangModuleFiles ccmf(clangImporter->getClangPreprocessor());
-
   Module *underlying = nullptr;
   if (options.ImportUnderlyingModule) {
     underlying = clangImporter->loadModule(SourceLoc(),