ash: Drop the immediately following power button released induced forcing off request

ash/system/chromeos/power/tablet_power_button_controller.cc

Index: ash/system/chromeos/power/tablet_power_button_controller.cc
diff --git a/ash/system/chromeos/power/tablet_power_button_controller.cc b/ash/system/chromeos/power/tablet_power_button_controller.cc
index cb316de4c38c476672dec7963eefd3946c0c7ac4..d5c4413705fbddb293ca8f483d3ff440ae6086fc 100644
--- a/ash/system/chromeos/power/tablet_power_button_controller.cc
+++ b/ash/system/chromeos/power/tablet_power_button_controller.cc
@@ -35,6 +35,10 @@ constexpr int kShutdownWhenScreenOffTimeoutMs = 2000;
 // ignored.
 constexpr int kIgnorePowerButtonAfterResumeMs = 2000;
 
+// Amount of time since last power button released that power button released
+// event for forcing off needs to be ignored.
+constexpr int kIgnoreReleasedAfterLastOneMs = 500;

[Daniel Erat, 2017/01/30 17:55:00]

nit: kIgnoreRepeatedButtonUpMs or something similar?

i'd also change the comment to something like:

// Ignore button-up events occurring within this many milliseconds
// of the previous button-up event. This prevents us from falling
// behind if the power button is pressed repeatedly.

[Qiang(Joe) Xu, 2017/01/30 19:35:43]

done, thanks!

+
 // Returns true if device is a convertible/tablet device, otherwise false.
 bool IsTabletModeSupported() {
   MaximizeModeController* maximize_mode_controller =
@@ -73,6 +77,7 @@ TabletPowerButtonController::TabletPowerButtonController(
     LockStateController* controller)
     : tick_clock_(new base::DefaultTickClock()),
       last_resume_time_(base::TimeTicks()),
+      last_released_time_(base::TimeTicks()),

[Daniel Erat, 2017/01/30 17:55:00]

i don't think you need to initialize this member and last_resume_time_
explicitly; they should automatically be constructed with the zero value.

[Qiang(Joe) Xu, 2017/01/30 19:35:44]

Done.

       force_off_on_button_up_(true),
       controller_(controller),
       weak_ptr_factory_(this) {
@@ -119,6 +124,20 @@ void TabletPowerButtonController::OnPowerButtonEvent(
     SetDisplayForcedOff(false);
     StartShutdownTimer();
   } else {
+    // When power button is released, cancel shutdown animation whenever it is
+    // still cancellable.
+    if (controller_->CanCancelShutdownAnimation())
+      controller_->CancelShutdownAnimation();
+

[Daniel Erat, 2017/01/30 17:55:00]

might be a little cleaner to do something like this:

  const base::TimeTicks previous_up_time = last_button_up_time_;
  last_button_up_time_ = tick_clock_->NowTicks();

  if (timestamp - previous_up_time <= ...) {
    shutdown_timer_.Stop();
    return;
  }

then the member is only updated by a single statement, which feels a bit
simpler.

[Qiang(Joe) Xu, 2017/01/30 19:35:43]

Done.

+    // Drop the very adjacent power button released event for forcing off.

[Daniel Erat, 2017/01/30 17:55:00]

maybe:

  // Ignore the event if it comes too soon after the last one.

?

[Qiang(Joe) Xu, 2017/01/30 19:35:43]

Done.

+    if (timestamp - last_released_time_ <=
+        base::TimeDelta::FromMilliseconds(kIgnoreReleasedAfterLastOneMs)) {
+      last_released_time_ = tick_clock_->NowTicks();
+      shutdown_timer_.Stop();
+      return;
+    }
+    last_released_time_ = tick_clock_->NowTicks();
+
     if (shutdown_timer_.IsRunning()) {
       shutdown_timer_.Stop();
       if (!screen_off_when_power_button_down_ && force_off_on_button_up_) {
@@ -126,11 +145,6 @@ void TabletPowerButtonController::OnPowerButtonEvent(
         LockScreenIfRequired();
       }
     }
-
-    // When power button is released, cancel shutdown animation whenever it is
-    // still cancellable.
-    if (controller_->CanCancelShutdownAnimation())
-      controller_->CancelShutdownAnimation();
   }
 }