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/Core/Event.cpp b/lldb/source/Core/Event.cpp
index 85da9b8..bd57198 100644
--- a/lldb/source/Core/Event.cpp
+++ b/lldb/source/Core/Event.cpp
@@ -64,7 +64,7 @@
                 static_cast<const void *>(this),
                 static_cast<void *>(broadcaster),
                 broadcaster->GetBroadcasterName().GetCString(), m_type,
-                event_name.GetString().c_str());
+                event_name.GetData());
     else
       s->Printf("%p Event: broadcaster = %p (%s), type = 0x%8.8x, data = ",
                 static_cast<const void *>(this),