This cl refactor TaskQueues to use a PIMPL implementation on linux/An…

…droid.

In later steps the Win/Mac implementation will also be refactored.

The rtc_task_queue target is split up in three separate targets:

rtc_task_queue_api:
Contains the header file task_queue.h but no implementation.
Only external TaskQueue implementations should directly depend on this target.

rtc_task_queue_impl:
Contains the default implementation of task_queue.h.
Only external application targets should directly depend on this target.

rtc_task_queue:
WebRTC targets should depend on this target. It unconditionally depend on rtc_task_queue_api and depending on the new build flag,|rtc_link_task_queue_impl|,  depend on rtc_task_queue_impl.

BUG=webrtc:8160

Review-Url: https://codereview.webrtc.org/3003643002
Cr-Commit-Position: refs/heads/master@{#19516}

webrtc/rtc_base/BUILD.gn

@@ -295,42 +295,71 @@ config("enable_libevent_config") {
   defines = [ "WEBRTC_BUILD_LIBEVENT" ]
 }
 
-rtc_static_library("rtc_task_queue") {
+rtc_source_set("rtc_task_queue") {
   public_deps = [
     ":rtc_base_approved",
+    ":rtc_task_queue_api",
   ]
 
+  if (rtc_link_task_queue_impl) {
+    deps = [
+      ":rtc_task_queue_impl",
+    ]
+  }
+}
+
+# WebRTC targets must not directly depend on rtc_task_queue_api or
+# rtc_task_queue_impl. Instead, depend on rtc_task_queue.
+# The build flag |rtc_link_task_queue_impl| decides if WebRTC targets will link
+# to the default implemenation in rtc_task_queue_impl or if an externally
+# provided implementation should be used. An external implementation should
+# depend on rtc_task_queue_api.
+rtc_source_set("rtc_task_queue_api") {
   if (build_with_chromium) {
     sources = [
-      "../../webrtc_overrides/webrtc/rtc_base/task_queue.cc",
       "../../webrtc_overrides/webrtc/rtc_base/task_queue.h",
     ]
   } else {
     sources = [
       "task_queue.h",
-      "task_queue_posix.h",
     ]
+  }
+  deps = [
+    ":rtc_base_approved",
+  ]
+}
+
+rtc_source_set("rtc_task_queue_impl") {
+  deps = [
+    ":rtc_base_approved",
+    ":rtc_task_queue_api",
+  ]
+  if (build_with_chromium) {
+    sources = [
+      "../../webrtc_overrides/webrtc/rtc_base/task_queue.cc",
+    ]
+  } else {
     if (rtc_build_libevent) {
-      deps = [
-        "//base/third_party/libevent",
-      ]
+      deps += [ "//base/third_party/libevent" ]
     }
-
     if (rtc_enable_libevent) {
-      sources += [
+      sources = [
         "task_queue_libevent.cc",
         "task_queue_posix.cc",
+        "task_queue_posix.h",
       ]
       all_dependent_configs = [ ":enable_libevent_config" ]
     } else {
       if (is_mac || is_ios) {
-        sources += [
+        sources = [
           "task_queue_gcd.cc",
           "task_queue_posix.cc",
         ]
       }
       if (is_win) {
-        sources += [ "task_queue_win.cc" ]
+        sources = [
+          "task_queue_win.cc",
+        ]
       }
     }
   }

webrtc/rtc_base/task_queue.h

@@ -15,23 +15,16 @@
 #include <memory>
 #include <queue>
 
-#if defined(WEBRTC_MAC) && !defined(WEBRTC_BUILD_LIBEVENT)
+#if defined(WEBRTC_MAC)
 #include <dispatch/dispatch.h>
 #endif
 
 #include "webrtc/rtc_base/constructormagic.h"
 #include "webrtc/rtc_base/criticalsection.h"
-
-#if defined(WEBRTC_WIN) || defined(WEBRTC_BUILD_LIBEVENT)
-#include "webrtc/rtc_base/platform_thread.h"
-#endif
-
-#if defined(WEBRTC_BUILD_LIBEVENT)
-#include "webrtc/rtc_base/refcountedobject.h"
 #include "webrtc/rtc_base/scoped_ref_ptr.h"
 
-struct event_base;
-struct event;
+#if defined(WEBRTC_WIN)
+#include "webrtc/rtc_base/platform_thread.h"
 #endif
 
 namespace rtc {
@@ -242,32 +235,7 @@ class LOCKABLE TaskQueue {
   }
 
  private:
-#if defined(WEBRTC_BUILD_LIBEVENT)
-  static void ThreadMain(void* context);
-  static void OnWakeup(int socket, short flags, void* context);  // NOLINT
-  static void RunTask(int fd, short flags, void* context);       // NOLINT
-  static void RunTimer(int fd, short flags, void* context);      // NOLINT
-
-  class ReplyTaskOwner;
-  class PostAndReplyTask;
-  class SetTimerTask;
-
-  typedef RefCountedObject<ReplyTaskOwner> ReplyTaskOwnerRef;
-
-  void PrepareReplyTask(scoped_refptr<ReplyTaskOwnerRef> reply_task);
-
-  struct QueueContext;
-
-  int wakeup_pipe_in_ = -1;
-  int wakeup_pipe_out_ = -1;
-  event_base* event_base_;
-  std::unique_ptr<event> wakeup_event_;
-  PlatformThread thread_;
-  rtc::CriticalSection pending_lock_;
-  std::list<std::unique_ptr<QueuedTask>> pending_ GUARDED_BY(pending_lock_);
-  std::list<scoped_refptr<ReplyTaskOwnerRef>> pending_replies_
-      GUARDED_BY(pending_lock_);
-#elif defined(WEBRTC_MAC)
+#if defined(WEBRTC_MAC)
   struct QueueContext;
   struct TaskContext;
   struct PostTaskAndReplyContext;
@@ -295,7 +263,8 @@ class LOCKABLE TaskQueue {
   std::queue<std::unique_ptr<QueuedTask>> pending_ GUARDED_BY(pending_lock_);
   HANDLE in_queue_;
 #else
-#error not supported.
+  class Impl;
+  const scoped_refptr<Impl> impl_;
 #endif
 
   RTC_DISALLOW_COPY_AND_ASSIGN(TaskQueue);