[NativePDB] Add a FromCompilerDecl for going from lldb -> clang

[lanza]

Summary

A common transformation in NativePDB is to go from lldb types to clang
types and vice versa. This function automates one of those steps.

[lanza]

fix typo

[lanza]

update

[lanza]

update

[aleksandr.urakov]

LGTM!

[lanza]

rebase

lldb/trunk/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.h

public:
   clang::QualType GetOrCreateType(PdbTypeSymId type);
 
   bool CompleteTagDecl(clang::TagDecl &tag);
   bool CompleteType(clang::QualType qt);
 
   CompilerDecl ToCompilerDecl(clang::Decl &decl);
   CompilerType ToCompilerType(clang::QualType qt);
   CompilerDeclContext ToCompilerDeclContext(clang::DeclContext &context);
+  clang::Decl * FromCompilerDecl(CompilerDecl decl);
   clang::DeclContext *FromCompilerDeclContext(CompilerDeclContext context);
 
   ClangASTContext &clang() { return m_clang; }
   ClangASTImporter &importer() { return m_importer; }
 
   void Dump(Stream &stream);
 
 private:

lldb/trunk/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp

CompilerType PdbAstBuilder::ToCompilerType(clang::QualType qt) {
   return {&m_clang, qt.getAsOpaquePtr()};
 }
 
 CompilerDeclContext
 PdbAstBuilder::ToCompilerDeclContext(clang::DeclContext &context) {
   return {&m_clang, &context};
 }
 
+clang::Decl * PdbAstBuilder::FromCompilerDecl(CompilerDecl decl) {
+  return static_cast<clang::Decl *>(decl.GetOpaqueDecl());
+}
+
 clang::DeclContext *
 PdbAstBuilder::FromCompilerDeclContext(CompilerDeclContext context) {
   return static_cast<clang::DeclContext *>(context.GetOpaqueDeclContext());
 }
 
 void PdbAstBuilder::Dump(Stream &stream) { m_clang.Dump(stream); }