add a simplified lexer ctor that sets up the lexer to raw-lex an
entire file.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62414 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/CacheTokens.cpp b/Driver/CacheTokens.cpp
index d447b90..7aa63b3 100644
--- a/Driver/CacheTokens.cpp
+++ b/Driver/CacheTokens.cpp
@@ -486,8 +486,7 @@
     if (!B) continue;
 
     FileID FID = SM.createFileID(FE, SourceLocation(), SrcMgr::C_User);
-    Lexer L(SM.getLocForStartOfFile(FID), LOpts,
-            B->getBufferStart(), B->getBufferEnd(), B);
+    Lexer L(FID, SM, LOpts);
     PM[FE] = LexTokens(L);
   }