Introduce command line option -dump-deserialized-decls which is used to print the PCH decls that got deserialized, for testing purposes.

llvm-svn: 116503
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index e3ba54c..8f0cb08 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1409,6 +1409,7 @@
   Opts.UsePredefines = !Args.hasArg(OPT_undef);
   Opts.DetailedRecord = Args.hasArg(OPT_detailed_preprocessing_record);
   Opts.DisablePCHValidation = Args.hasArg(OPT_fno_validate_pch);
+  Opts.DumpDeserializedPCHDecls = Args.hasArg(OPT_dump_deserialized_pch_decls);
 
   if (const Arg *A = Args.getLastArg(OPT_preamble_bytes_EQ)) {
     llvm::StringRef Value(A->getValue(Args));