Change raw_svector_ostream to reserve the input buffer if necessary, Ted was

right.
 - This class turns out to be much more convenient to use if we do this; clients
   can make sure the buffer is always big enough if they care (since our current
   idiom tends to be to use a SmallString<256> for the input to this we should
   generally be avoiding an unnecessary malloc).

Also, add a convenience raw_svector_ostream::str method which flushes the buffer
and returns a StringRef for the vector contents.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79446 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/raw_ostream.h

@@ -454,10 +454,14 @@ class raw_svector_ostream : public raw_ostream {
 public:
   /// Construct a new raw_svector_ostream.
   ///
-  /// \arg O - The vector to write to; this *must* have at least 128 bytes of
-  /// free space in it.
+  /// \arg O - The vector to write to; this should generally have at least 128
+  /// bytes free to avoid any extraneous memory overhead.
   explicit raw_svector_ostream(SmallVectorImpl<char> &O);
   ~raw_svector_ostream();
+
+  /// str - Flushes the stream contents to the target vector and return a
+  /// StringRef for the vector contents.
+  StringRef str();
 };
 
 /// raw_null_ostream - A raw_ostream that discards all output.