Make the Error class constructor protected

This is forcing to use Error::success(), which is in a wide majority
of cases a lot more readable.

Differential Revision: https://reviews.llvm.org/D26481

llvm-svn: 286561
diff --git a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
index 46d8df8..5b390d8 100644
--- a/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
+++ b/lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp
@@ -133,7 +133,7 @@
 
 uint32_t ProcessMinidump::GetPluginVersion() { return 1; }
 
-Error ProcessMinidump::DoDestroy() { return Error(); }
+Error ProcessMinidump::DoDestroy() { return Error::success(); }
 
 void ProcessMinidump::RefreshStateAfterStop() {
   if (!m_active_exception)