[circular_raw_ostream] Delegate is_displayed to contained stream

raw_ostream has an is_displayed() member function that determines if the stream
is connected to a console for display or is connected to a file/pipe. By
default, is_displayed() returns false, and derived classes like raw_fd_ostream
override it. Because circular_raw_ostream wraps another stream, its result for
is_displayed() should be the same as that stream.

Differential Revision: https://reviews.llvm.org/D66026

llvm-svn: 369188

llvm/include/llvm/Support/circular_raw_ostream.h

@@ -122,6 +122,10 @@ namespace llvm {
       delete[] BufferArray;
     }
 
+    bool is_displayed() const override {
+      return TheStream->is_displayed();
+    }
+
     /// setStream - Tell the circular_raw_ostream to output a
     /// different stream.  "Owns" tells circular_raw_ostream whether
     /// it should take responsibility for managing the underlying