Remove dependency from raw_ostream on <chrono>

The tryLockFor method from raw_fd_sotreamis the sole user of that
header, and it's not referenced in the mono repo. I still chose to keep
it (may be useful for downstream user) but added a transient type that's
forward declared to hold the duration parameter.

Notable changes:

- "llvm/Support/Duration.h" must be included in order to use tryLockFor.
- "llvm/Support/raw_ostream.h" no longer includes <chrono>

This sole change has an interesting impact on the number of processed
line, as measured by:

clang++ -E  -Iinclude -I../llvm/include ../llvm/lib/Support/*.cpp -std=c++14 -fno-rtti -fno-exceptions | wc -l

before: 7917500
after:  7835142

Discourse thread on the topic: https://llvm.discourse.group/t/include-what-you-use-include-cleanup/5831

lldb/tools/lldb-vscode/FifoFiles.h

@@ -14,6 +14,8 @@
 
 #include "JSONUtils.h"
 
+#include <chrono>
+
 namespace lldb_vscode {
 
 /// Struct that controls the life of a fifo file in the filesystem.

llvm/include/llvm/Debuginfod/Debuginfod.h

@@ -23,6 +23,8 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBuffer.h"
 
+#include <chrono>
+
 namespace llvm {
 
 typedef ArrayRef<uint8_t> BuildIDRef;

llvm/include/llvm/Debuginfod/HTTPClient.h

@@ -19,6 +19,8 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBuffer.h"
 
+#include <chrono>
+
 namespace llvm {
 
 enum class HTTPMethod { GET };

llvm/include/llvm/Support/Duration.h

@@ -0,0 +1,28 @@
+//===--- Duration.h - wrapper around std::chrono::Duration ------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  The sole purpose of this file is to avoid the dependency on <chrono> in
+//  raw_ostream.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_DURATION_H
+#define LLVM_SUPPORT_DURATION_H
+
+#include <chrono>
+
+namespace llvm {
+class Duration {
+  std::chrono::milliseconds Value;
+  public:
+  Duration(std::chrono::milliseconds Value) : Value(Value) {}
+  std::chrono::milliseconds getDuration() const { return Value; }
+};
+}
+
+#endif

llvm/include/llvm/Support/raw_ostream.h

@@ -17,7 +17,6 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/DataTypes.h"
 #include <cassert>
-#include <chrono>
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
@@ -30,6 +29,7 @@
 
 namespace llvm {
 
+class Duration;
 class formatv_object_base;
 class format_object_base;
 class FormattedString;
@@ -574,7 +574,7 @@ public:
   ///
   /// It is used as @ref lock.
   LLVM_NODISCARD
-  Expected<sys::fs::FileLocker> tryLockFor(std::chrono::milliseconds Timeout);
+  Expected<sys::fs::FileLocker> tryLockFor(Duration const& Timeout);
 };
 
 /// This returns a reference to a raw_fd_ostream for standard output. Use it

llvm/lib/Support/raw_ostream.cpp

@@ -15,6 +15,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Config/config.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/Duration.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Format.h"
@@ -868,8 +869,8 @@ Expected<sys::fs::FileLocker> raw_fd_ostream::lock() {
 }
 
 Expected<sys::fs::FileLocker>
-raw_fd_ostream::tryLockFor(std::chrono::milliseconds Timeout) {
-  std::error_code EC = sys::fs::tryLockFile(FD, Timeout);
+raw_fd_ostream::tryLockFor(Duration const& Timeout) {
+  std::error_code EC = sys::fs::tryLockFile(FD, Timeout.getDuration());
   if (!EC)
     return sys::fs::FileLocker(FD);
   return errorCodeToError(EC);

llvm/unittests/Support/Path.cpp

@@ -15,6 +15,7 @@
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/ConvertUTF.h"
+#include "llvm/Support/Duration.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"