[Reproducers] Make clang use lldb's VFS.

In r353906 we hooked up clang and lldb's reproducer infrastructure to
capture files used by clang. This patch adds the necessary logic to have
clang reuse the files from lldb's reproducer during replay.

Differential revision: https://reviews.llvm.org/D58309

llvm-svn: 354283
diff --git a/lldb/unittests/Language/Highlighting/HighlighterTest.cpp b/lldb/unittests/Language/Highlighting/HighlighterTest.cpp
index 1faf226..8426712 100644
--- a/lldb/unittests/Language/Highlighting/HighlighterTest.cpp
+++ b/lldb/unittests/Language/Highlighting/HighlighterTest.cpp
@@ -9,6 +9,7 @@
 #include "gtest/gtest.h"
 
 #include "lldb/Core/Highlighter.h"
+#include "lldb/Host/FileSystem.h"
 
 #include "Plugins/Language/CPlusPlus/CPlusPlusLanguage.h"
 #include "Plugins/Language/ObjC/ObjCLanguage.h"
@@ -27,6 +28,7 @@
 void HighlighterTest::SetUpTestCase() {
   // The HighlighterManager uses the language plugins under the hood, so we
   // have to initialize them here for our test process.
+  FileSystem::Initialize();
   CPlusPlusLanguage::Initialize();
   ObjCLanguage::Initialize();
   ObjCPlusPlusLanguage::Initialize();
@@ -36,6 +38,7 @@
   CPlusPlusLanguage::Terminate();
   ObjCLanguage::Terminate();
   ObjCPlusPlusLanguage::Terminate();
+  FileSystem::Terminate();
 }
 
 static std::string getName(lldb::LanguageType type) {