Refactor Subzero initialization and add a browser callback handler.

src/IceCompileServer.cpp

+//===- subzero/src/IceCompileServer.cpp - Compile server ------------------===//
+//
+//                        The Subzero Code Generator
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the basic commandline-based compile server.
+//
+//===----------------------------------------------------------------------===//
+
+#include "IceCompileServer.h"
+
+#include <thread>
+
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/raw_os_ostream.h"
+#include "llvm/Support/StreamingMemoryObject.h"
+
+namespace Ice {
+
+// Command-line variant.
+
+void CLCompileServer::run() {
+  std::thread CompileThread([this]() { getCompiler().run(argc, argv, *this); });
+  CompileThread.join();
+}
+
+std::unique_ptr<llvm::DataStreamer>
+CLCompileServer::getInputStream(const IceString &InputFilename,
+                                std::string &ErrorString) {
+  std::unique_ptr<llvm::DataStreamer> Result(
+      llvm::getDataFileStreamer(InputFilename, &ErrorString));
+  return std::move(Result);
+}
+
+std::unique_ptr<llvm::raw_fd_ostream>
+CLCompileServer::getOutputStream(const IceString &OutputFilename,
+                                 std::error_code &EC) {
+  std::unique_ptr<llvm::raw_fd_ostream> Result(
+      new llvm::raw_fd_ostream(OutputFilename, EC, llvm::sys::fs::F_None));
+  return std::move(Result);
+}
+
+} // end of namespace Ice