Add a little more data to chained PCHs. WIP

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108528 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/GeneratePCH.cpp b/lib/Frontend/GeneratePCH.cpp
index 2f3df94..422a4b6 100644
--- a/lib/Frontend/GeneratePCH.cpp
+++ b/lib/Frontend/GeneratePCH.cpp
@@ -54,7 +54,10 @@
   // Install a stat() listener to keep track of all of the stat()
   // calls.
   StatCalls = new MemorizeStatCalls;
-  PP.getFileManager().addStatCache(StatCalls, /*AtBeginning=*/true);
+  // If we have a chain, we want new stat calls only, so install the memorizer
+  // *after* the already installed PCHReader's stat cache.
+  PP.getFileManager().addStatCache(StatCalls,
+    /*AtBeginning=*/!Chain);
 }
 
 void PCHGenerator::HandleTranslationUnit(ASTContext &Ctx) {