Use ErrorOr for the ::create factory on instrumented and sample profilers.

Summary:
As discussed in
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20141027/242445.html,
the creation of reader and writer instances is better done using
ErrorOr. There are no functional changes, but several callers needed to
be adjusted.

Reviewers: bogner

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6076

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221120 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ProfileData/InstrProfReader.h

@@ -18,6 +18,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ProfileData/InstrProf.h"
+#include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/LineIterator.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/EndianStream.h"
@@ -94,8 +95,7 @@ public:
 
   /// Factory method to create an appropriately typed reader for the given
   /// instrprof file.
-  static std::error_code create(std::string Path,
-                                std::unique_ptr<InstrProfReader> &Result);
+  static ErrorOr<std::unique_ptr<InstrProfReader>> create(std::string Path);
 };
 
 /// Reader for the simple text based instrprof format.