make "ContentCache::Buffer" mutable to avoid a const_cast.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62403 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index fa0a9bb..1240262 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -56,9 +56,7 @@
   if (!Buffer && Entry) {
     // FIXME: Should we support a way to not have to do this check over
     //   and over if we cannot open the file?
-    // FIXME: This const_cast is ugly.  Should we make getBuffer() non-const?
-    const_cast<ContentCache*>(this)->Buffer = 
-      MemoryBuffer::getFile(Entry->getName(), 0, Entry->getSize());
+    Buffer = MemoryBuffer::getFile(Entry->getName(), 0, Entry->getSize());
   }
 #endif
   return Buffer;