Refactor base::Timer to not call TimeTicks::Now for task with 0 delay.

This CL remove the calls to TimeTicks::Now when a timer is called with a
delay null or negative. The reason is that TimeTicks::Now is costly on
Android and is not useful in that use case.

R=mark@chromium.org
BUG=315070

Review URL: https://codereview.chromium.org/105003002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238741 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 19 insertions, 8 deletions

diff --git a/base/timer/timer.cc b/base/timer/timer.cc
index aafc01e..1c4b10c6d 100644
--- a/base/timer/timer.cc
+++ b/base/timer/timer.cc
@@ -108,11 +108,14 @@ void Timer::Reset() {
   }
 
   // Set the new desired_run_time_.
-  desired_run_time_ = TimeTicks::Now() + delay_;
+  if (delay_ > TimeDelta::FromMicroseconds(0))
+    desired_run_time_ = TimeTicks::Now() + delay_;
+  else
+    desired_run_time_ = TimeTicks();
 
   // We can use the existing scheduled task if it arrives before the new
   // desired_run_time_.
-  if (desired_run_time_ > scheduled_run_time_) {
+  if (desired_run_time_ >= scheduled_run_time_) {
     is_running_ = true;
     return;
   }
@@ -134,10 +137,16 @@ void Timer::PostNewScheduledTask(TimeDelta delay) {
   DCHECK(scheduled_task_ == NULL);
   is_running_ = true;
   scheduled_task_ = new BaseTimerTaskInternal(this);
-  ThreadTaskRunnerHandle::Get()->PostDelayedTask(posted_from_,
-      base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_)),
-      delay);
-  scheduled_run_time_ = desired_run_time_ = TimeTicks::Now() + delay;
+  if (delay > TimeDelta::FromMicroseconds(0)) {
+    ThreadTaskRunnerHandle::Get()->PostDelayedTask(posted_from_,
+        base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_)),
+        delay);
+    scheduled_run_time_ = desired_run_time_ = TimeTicks::Now() + delay;
+  } else {
+    ThreadTaskRunnerHandle::Get()->PostTask(posted_from_,
+        base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_)));
+    scheduled_run_time_ = desired_run_time_ = TimeTicks();
+  }
   // Remember the thread ID that posts the first task -- this will be verified
   // later when the task is abandoned to detect misuse from multiple threads.
   if (!thread_id_)
diff --git a/base/timer/timer.h b/base/timer/timer.h
index f952d41..71a7ae8 100644
--- a/base/timer/timer.h
+++ b/base/timer/timer.h
@@ -148,7 +148,8 @@ class BASE_EXPORT Timer {
   base::Closure user_task_;
 
   // The estimated time that the MessageLoop will run the scheduled_task_ that
-  // will call RunScheduledTask().
+  // will call RunScheduledTask(). This time can be a "zero" TimeTicks if the
+  // task must be run immediately.
   TimeTicks scheduled_run_time_;
 
   // The desired run time of user_task_. The user may update this at any time,
@@ -156,7 +157,8 @@ class BASE_EXPORT Timer {
   // greater than scheduled_run_time_, a continuation task will be posted to
   // wait for the remaining time. This allows us to reuse the pending task so as
   // not to flood the MessageLoop with orphaned tasks when the user code
-  // excessively Stops and Starts the timer.
+  // excessively Stops and Starts the timer. This time can be a "zero" TimeTicks
+  // if the task must be run immediately.
   TimeTicks desired_run_time_;
 
   // Thread ID of current MessageLoop for verifying single-threaded usage.