Revert "IRGen: Start using the WriteThinLTOBitcode pass."

Summary:
This reverts commit r292662.

This change broke internal builds. Will provide a reproducer internally.

Subscribers: pcc, mehdi_amini, cfe-commits, mgorny

Differential Revision: https://reviews.llvm.org/D29025

llvm-svn: 292791
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 4fdffde..bac1e89 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -689,11 +689,9 @@
     break;
 
   case Backend_EmitBC:
-    if (CodeGenOpts.EmitSummaryIndex)
-      PerModulePasses.add(createWriteThinLTOBitcodePass(*OS));
-    else
-      PerModulePasses.add(
-          createBitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists));
+    PerModulePasses.add(createBitcodeWriterPass(
+        *OS, CodeGenOpts.EmitLLVMUseLists, CodeGenOpts.EmitSummaryIndex,
+        CodeGenOpts.EmitSummaryIndex));
     break;
 
   case Backend_EmitLL: