Reland "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)

Reland the base->rtc_base without adding stub headers (will be
done in follow-up CL). This preserves git blame history of all files.

BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org

Change-Id: Iea3bb6f3f67b8374c96337b63e8f5aa3e6181012
Reviewed-on: https://chromium-review.googlesource.com/554611
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18821}

webrtc/rtc_base/platform_thread.h

@@ -0,0 +1,124 @@
+/*
+ *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_RTC_BASE_PLATFORM_THREAD_H_
+#define WEBRTC_RTC_BASE_PLATFORM_THREAD_H_
+
+#include <string>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/base/event.h"
+#include "webrtc/base/platform_thread_types.h"
+#include "webrtc/base/thread_checker.h"
+
+namespace rtc {
+
+PlatformThreadId CurrentThreadId();
+PlatformThreadRef CurrentThreadRef();
+
+// Compares two thread identifiers for equality.
+bool IsThreadRefEqual(const PlatformThreadRef& a, const PlatformThreadRef& b);
+
+// Sets the current thread name.
+void SetCurrentThreadName(const char* name);
+
+// Callback function that the spawned thread will enter once spawned.
+// A return value of false is interpreted as that the function has no
+// more work to do and that the thread can be released.
+typedef bool (*ThreadRunFunctionDeprecated)(void*);
+typedef void (*ThreadRunFunction)(void*);
+
+enum ThreadPriority {
+#ifdef WEBRTC_WIN
+  kLowPriority = THREAD_PRIORITY_BELOW_NORMAL,
+  kNormalPriority = THREAD_PRIORITY_NORMAL,
+  kHighPriority = THREAD_PRIORITY_ABOVE_NORMAL,
+  kHighestPriority = THREAD_PRIORITY_HIGHEST,
+  kRealtimePriority = THREAD_PRIORITY_TIME_CRITICAL
+#else
+  kLowPriority = 1,
+  kNormalPriority = 2,
+  kHighPriority = 3,
+  kHighestPriority = 4,
+  kRealtimePriority = 5
+#endif
+};
+
+// Represents a simple worker thread.  The implementation must be assumed
+// to be single threaded, meaning that all methods of the class, must be
+// called from the same thread, including instantiation.
+class PlatformThread {
+ public:
+  PlatformThread(ThreadRunFunctionDeprecated func,
+                 void* obj,
+                 const char* thread_name);
+  PlatformThread(ThreadRunFunction func,
+                 void* obj,
+                 const char* thread_name,
+                 ThreadPriority priority = kNormalPriority);
+  virtual ~PlatformThread();
+
+  const std::string& name() const { return name_; }
+
+  // Spawns a thread and tries to set thread priority according to the priority
+  // from when CreateThread was called.
+  void Start();
+
+  bool IsRunning() const;
+
+  // Returns an identifier for the worker thread that can be used to do
+  // thread checks.
+  PlatformThreadRef GetThreadRef() const;
+
+  // Stops (joins) the spawned thread.
+  void Stop();
+
+  // Set the priority of the thread. Must be called when thread is running.
+  // TODO(tommi): Make private and only allow public support via ctor.
+  bool SetPriority(ThreadPriority priority);
+
+ protected:
+#if defined(WEBRTC_WIN)
+  // Exposed to derived classes to allow for special cases specific to Windows.
+  bool QueueAPC(PAPCFUNC apc_function, ULONG_PTR data);
+#endif
+
+ private:
+  void Run();
+
+  ThreadRunFunctionDeprecated const run_function_deprecated_ = nullptr;
+  ThreadRunFunction const run_function_ = nullptr;
+  const ThreadPriority priority_ = kNormalPriority;
+  void* const obj_;
+  // TODO(pbos): Make sure call sites use string literals and update to a const
+  // char* instead of a std::string.
+  const std::string name_;
+  rtc::ThreadChecker thread_checker_;
+  rtc::ThreadChecker spawned_thread_checker_;
+#if defined(WEBRTC_WIN)
+  static DWORD WINAPI StartThread(void* param);
+
+  bool stop_ = false;
+  HANDLE thread_ = nullptr;
+  DWORD thread_id_ = 0;
+#else
+  static void* StartThread(void* param);
+
+  // An atomic flag that we use to stop the thread. Only modified on the
+  // controlling thread and checked on the worker thread.
+  volatile int stop_flag_ = 0;
+  pthread_t thread_ = 0;
+#endif  // defined(WEBRTC_WIN)
+  RTC_DISALLOW_COPY_AND_ASSIGN(PlatformThread);
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_RTC_BASE_PLATFORM_THREAD_H_