Index: include/clang/Tooling/Tooling.h
===================================================================
--- include/clang/Tooling/Tooling.h
+++ include/clang/Tooling/Tooling.h
@@ -187,6 +187,15 @@
         std::make_shared<PCHContainerOperations>(),
     const FileContentMappings &VirtualMappedFiles = FileContentMappings());
 
+// Similar to the overload except this takes a VFS.
+bool runToolOnCodeWithArgs(
+    FrontendAction *ToolAction, const Twine &Code,
+    llvm::IntrusiveRefCntPtr<vfs::FileSystem> VFS,
+    const std::vector<std::string> &Args, const Twine &FileName = "input.cc",
+    const Twine &ToolName = "clang-tool",
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps =
+        std::make_shared<PCHContainerOperations>());
+
 /// Builds an AST for 'Code'.
 ///
 /// \param Code C++ code.
Index: lib/Tooling/Tooling.cpp
===================================================================
--- lib/Tooling/Tooling.cpp
+++ lib/Tooling/Tooling.cpp
@@ -155,27 +155,37 @@
 
 bool runToolOnCodeWithArgs(
     FrontendAction *ToolAction, const Twine &Code,
+    llvm::IntrusiveRefCntPtr<vfs::FileSystem> VFS,
     const std::vector<std::string> &Args, const Twine &FileName,
     const Twine &ToolName,
-    std::shared_ptr<PCHContainerOperations> PCHContainerOps,
-    const FileContentMappings &VirtualMappedFiles) {
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps) {
   SmallString<16> FileNameStorage;
   StringRef FileNameRef = FileName.toNullTerminatedStringRef(FileNameStorage);
-  llvm::IntrusiveRefCntPtr<vfs::OverlayFileSystem> OverlayFileSystem(
-      new vfs::OverlayFileSystem(vfs::getRealFileSystem()));
-  llvm::IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
-      new vfs::InMemoryFileSystem);
-  OverlayFileSystem->pushOverlay(InMemoryFileSystem);
+
   llvm::IntrusiveRefCntPtr<FileManager> Files(
-      new FileManager(FileSystemOptions(), OverlayFileSystem));
+      new FileManager(FileSystemOptions(), VFS));
   ArgumentsAdjuster Adjuster = getClangStripDependencyFileAdjuster();
   ToolInvocation Invocation(
       getSyntaxOnlyToolArgs(ToolName, Adjuster(Args, FileNameRef), FileNameRef),
       ToolAction, Files.get(),
       std::move(PCHContainerOps));
+  return Invocation.run();
+}
+
+bool runToolOnCodeWithArgs(
+    FrontendAction *ToolAction, const Twine &Code,
+    const std::vector<std::string> &Args, const Twine &FileName,
+    const Twine &ToolName,
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    const FileContentMappings &VirtualMappedFiles) {
+  llvm::IntrusiveRefCntPtr<vfs::OverlayFileSystem> OverlayFileSystem(
+      new vfs::OverlayFileSystem(vfs::getRealFileSystem()));
+  llvm::IntrusiveRefCntPtr<vfs::InMemoryFileSystem> InMemoryFileSystem(
+      new vfs::InMemoryFileSystem);
+  OverlayFileSystem->pushOverlay(InMemoryFileSystem);
 
   SmallString<1024> CodeStorage;
-  InMemoryFileSystem->addFile(FileNameRef, 0,
+  InMemoryFileSystem->addFile(FileName, 0,
                               llvm::MemoryBuffer::getMemBuffer(
                                   Code.toNullTerminatedStringRef(CodeStorage)));
 
@@ -185,7 +195,8 @@
         llvm::MemoryBuffer::getMemBuffer(FilenameWithContent.second));
   }
 
-  return Invocation.run();
+  return runToolOnCodeWithArgs(ToolAction, Code, OverlayFileSystem, Args,
+                               FileName, ToolName);
 }
 
 std::string getAbsolutePath(StringRef File) {