[lldb][NFC] Modernize ClangASTContext constructor

Now using default initializers and StringRef.

Also formats the member list that we excluded from clang-format
at some point and still hangs around with the old LLDB code style.

llvm-svn: 373329
diff --git a/lldb/source/Symbol/ClangASTContext.cpp b/lldb/source/Symbol/ClangASTContext.cpp
index 78bad39..891410d 100644
--- a/lldb/source/Symbol/ClangASTContext.cpp
+++ b/lldb/source/Symbol/ClangASTContext.cpp
@@ -522,14 +522,9 @@
   Opts.NoInlineDefine = !Opt;
 }
 
-ClangASTContext::ClangASTContext(const char *target_triple)
-    : TypeSystem(TypeSystem::eKindClang), m_target_triple(), m_ast_up(),
-      m_language_options_up(), m_source_manager_up(), m_diagnostics_engine_up(),
-      m_target_options_rp(), m_target_info_up(), m_identifier_table_up(),
-      m_selector_table_up(), m_builtins_up(), m_callback_tag_decl(nullptr),
-      m_callback_objc_decl(nullptr), m_callback_baton(nullptr),
-      m_pointer_byte_size(0), m_ast_owned(false) {
-  if (target_triple && target_triple[0])
+ClangASTContext::ClangASTContext(llvm::StringRef target_triple)
+    : TypeSystem(TypeSystem::eKindClang) {
+  if (!target_triple.empty())
     SetTargetTriple(target_triple);
 }
 
@@ -676,13 +671,13 @@
   return m_target_triple.c_str();
 }
 
-void ClangASTContext::SetTargetTriple(const char *target_triple) {
+void ClangASTContext::SetTargetTriple(llvm::StringRef target_triple) {
   Clear();
-  m_target_triple.assign(target_triple);
+  m_target_triple = target_triple.str();
 }
 
 void ClangASTContext::SetArchitecture(const ArchSpec &arch) {
-  SetTargetTriple(arch.GetTriple().str().c_str());
+  SetTargetTriple(arch.GetTriple().str());
 }
 
 bool ClangASTContext::HasExternalSource() {