Revert "Modules: Cache PCMs in memory and avoid a use-after-free"

This reverts commit r298165, as it broke the ARM builds.

llvm-svn: 298185
diff --git a/clang/unittests/Lex/LexerTest.cpp b/clang/unittests/Lex/LexerTest.cpp
index b5a6fd9..918167b 100644
--- a/clang/unittests/Lex/LexerTest.cpp
+++ b/clang/unittests/Lex/LexerTest.cpp
@@ -12,7 +12,6 @@
 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/LangOptions.h"
-#include "clang/Basic/MemoryBufferCache.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/TargetOptions.h"
@@ -65,12 +64,10 @@
     SourceMgr.setMainFileID(SourceMgr.createFileID(std::move(Buf)));
 
     VoidModuleLoader ModLoader;
-    MemoryBufferCache PCMCache;
     HeaderSearch HeaderInfo(std::make_shared<HeaderSearchOptions>(), SourceMgr,
                             Diags, LangOpts, Target.get());
     Preprocessor PP(std::make_shared<PreprocessorOptions>(), Diags, LangOpts,
-                    SourceMgr, PCMCache, HeaderInfo, ModLoader,
-                    /*IILookup =*/nullptr,
+                    SourceMgr, HeaderInfo, ModLoader, /*IILookup =*/nullptr,
                     /*OwnsHeaderSearch =*/false);
     PP.Initialize(*Target);
     PP.EnterMainSourceFile();