[base] Migrate MessagePumpLibEvent to DoSomeWork

This is a simple one and gets rid of a redundant call to
TimeTicks::Now() thanks to the new API :)

Bug: 885371
Change-Id: I3dccde418849992ad0bce18297c79eea6f98f072
Reviewed-on: https://chromium-review.googlesource.com/c/1485125
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Auto-Submit: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636910}

base/message_loop/message_pump_libevent.cc

@@ -205,36 +205,33 @@ void MessagePumpLibevent::Run(Delegate* delegate) {
     mac::ScopedNSAutoreleasePool autorelease_pool;
 #endif
 
-    bool did_work = delegate->DoWork();
+    Delegate::NextWorkInfo next_work_info = delegate->DoSomeWork();
+    bool more_work_is_plausible = next_work_info.is_immediate();
     if (!keep_running_)
       break;
 
     event_base_loop(event_base_, EVLOOP_NONBLOCK);
-    did_work |= processed_io_events_;
+    more_work_is_plausible |= processed_io_events_;
     processed_io_events_ = false;
     if (!keep_running_)
       break;
 
-    did_work |= delegate->DoDelayedWork(&delayed_work_time_);
-    if (!keep_running_)
-      break;
-
-    if (did_work)
+    if (more_work_is_plausible)
       continue;
 
-    did_work = delegate->DoIdleWork();
+    more_work_is_plausible = delegate->DoIdleWork();
     if (!keep_running_)
       break;
 
-    if (did_work)
+    if (more_work_is_plausible)
       continue;
 
     // EVLOOP_ONCE tells libevent to only block once,
     // but to service all pending events when it wakes up.
-    if (delayed_work_time_.is_null()) {
+    if (next_work_info.delayed_run_time.is_max()) {
       event_base_loop(event_base_, EVLOOP_ONCE);
     } else {
-      TimeDelta delay = delayed_work_time_ - TimeTicks::Now();
+      const TimeDelta delay = next_work_info.remaining_delay();
       if (delay > TimeDelta()) {
         struct timeval poll_tv;
         poll_tv.tv_sec = delay.InSeconds();
@@ -244,10 +241,6 @@ void MessagePumpLibevent::Run(Delegate* delegate) {
         event_add(timer_event.get(), &poll_tv);
         event_base_loop(event_base_, EVLOOP_ONCE);
         event_del(timer_event.get());
-      } else {
-        // It looks like delayed_work_time_ indicates a time in the past, so we
-        // need to call DoDelayedWork now.
-        delayed_work_time_ = TimeTicks();
       }
     }
 
@@ -272,10 +265,10 @@ void MessagePumpLibevent::ScheduleWork() {
 
 void MessagePumpLibevent::ScheduleDelayedWork(
     const TimeTicks& delayed_work_time) {
-  // We know that we can't be blocked on Wait right now since this method can
-  // only be called on the same thread as Run, so we only need to update our
-  // record of how long to sleep when we do sleep.
-  delayed_work_time_ = delayed_work_time;
+  // We know that we can't be blocked on Run()'s |timer_event| right now since
+  // this method can only be called on the same thread as Run(). Hence we have
+  // nothing to do here, this thread will sleep in Run() with the correct
+  // timeout when it's out of immediate tasks.
 }
 
 bool MessagePumpLibevent::Init() {

base/message_loop/message_pump_libevent.h

@@ -12,7 +12,6 @@
 #include "base/message_loop/message_pump.h"
 #include "base/message_loop/watchable_io_message_pump_posix.h"
 #include "base/threading/thread_checker.h"
-#include "base/time/time.h"
 
 // Declare structs we need from libevent.h rather than including it
 struct event_base;
@@ -100,9 +99,6 @@ class BASE_EXPORT MessagePumpLibevent : public MessagePump,
   // This flag is set if libevent has processed I/O events.
   bool processed_io_events_;
 
-  // The time at which we should call DoDelayedWork.
-  TimeTicks delayed_work_time_;
-
   // Libevent dispatcher.  Watches all sockets registered with it, and sends
   // readiness callbacks when a socket is ready for I/O.
   event_base* event_base_;

base/message_loop/message_pump_unittest.cc

@@ -4,13 +4,21 @@
 
 #include "base/message_loop/message_pump.h"
 
+#include <type_traits>
+
 #include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_pump_for_io.h"
+#include "base/message_loop/message_pump_for_ui.h"
 #include "base/test/bind_test_util.h"
 #include "base/threading/thread.h"
 #include "build/build_config.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+#if defined(OS_POSIX) && !defined(OS_NACL_SFI)
+#include "base/message_loop/message_pump_libevent.h"
+#endif
+
 using ::testing::_;
 using ::testing::AnyNumber;
 using ::testing::Invoke;
@@ -38,6 +46,10 @@ bool PumpTypeUsesDoSomeWork(MessageLoopBase::Type type) {
       return true;
 #elif defined(OS_WIN)
       return true;
+#elif defined(OS_POSIX) && !defined(OS_NACL_SFI)
+      // MessagePumpLibevent was migrated (ref. message_pump_for_ui.h and
+      // |use_libevent| in base/BUILD.gn for enabled conditions).
+      return std::is_same<MessagePumpForUI, MessagePumpLibevent>::value;
 #else
       // TODO(gab): Complete migration of all UI pumps to DoSomeWork() as part
       // of crbug.com/885371.
@@ -47,6 +59,10 @@ bool PumpTypeUsesDoSomeWork(MessageLoopBase::Type type) {
     case MessageLoopBase::Type::TYPE_IO:
 #if defined(OS_WIN) || (defined(OS_MACOSX) && !defined(OS_IOS))
       return true;
+#elif defined(OS_POSIX) && !defined(OS_NACL_SFI)
+      // MessagePumpLibevent was migrated (ref. message_pump_for_io.h and
+      // |use_libevent| in base/BUILD.gn for enabled conditions).
+      return std::is_same<MessagePumpForIO, MessagePumpLibevent>::value;
 #else
       // TODO(gab): Complete migration of all IO pumps to DoSomeWork() as part
       // of crbug.com/885371.