Don't allow direct access to StreamString's internal buffer.

This is a large API change that removes the two functions from
StreamString that return a std::string& and a const std::string&,
and instead provide one function which returns a StringRef.

Direct access to the underlying buffer violates the concept of
a "stream" which is intended to provide forward only access,
and makes porting to llvm::raw_ostream more difficult in the
future.

Differential Revision: https://reviews.llvm.org/D26698

llvm-svn: 287152
diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index fbf69d8..a695589 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -2463,20 +2463,20 @@
                   result.AppendErrorWithFormat(
                       "Unable to create the executable or symbol file with "
                       "UUID %s with path %s and symbol file %s",
-                      strm.GetString().c_str(),
+                      strm.GetData(),
                       module_spec.GetFileSpec().GetPath().c_str(),
                       module_spec.GetSymbolFileSpec().GetPath().c_str());
                 } else {
                   result.AppendErrorWithFormat(
                       "Unable to create the executable or symbol file with "
                       "UUID %s with path %s",
-                      strm.GetString().c_str(),
+                      strm.GetData(),
                       module_spec.GetFileSpec().GetPath().c_str());
                 }
               } else {
                 result.AppendErrorWithFormat("Unable to create the executable "
                                              "or symbol file with UUID %s",
-                                             strm.GetString().c_str());
+                                             strm.GetData());
               }
               result.SetStatus(eReturnStatusFailed);
               return false;
@@ -2486,7 +2486,7 @@
             module_spec.GetUUID().Dump(&strm);
             result.AppendErrorWithFormat(
                 "Unable to locate the executable or symbol file with UUID %s",
-                strm.GetString().c_str());
+                strm.GetData());
             result.SetStatus(eReturnStatusFailed);
             return false;
           }
@@ -4224,7 +4224,7 @@
             error_strm.PutCString(
                 "unable to find debug symbols for the current frame");
           }
-          result.AppendError(error_strm.GetData());
+          result.AppendError(error_strm.GetString());
         }
       } else {
         result.AppendError("one or more symbol file paths must be specified, "