Disable scheduler deadline task on battery power in Windows

cc/scheduler/scheduler_state_machine.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/scheduler/scheduler_state_machine.h"
 
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
@@ skipping 30 matching lines @@
       can_start_(false),
       can_draw_(false),
       has_pending_tree_(false),
       pending_tree_is_ready_for_activation_(false),
       active_tree_needs_first_draw_(false),
       did_commit_after_animating_(false),
       did_create_and_initialize_first_output_surface_(false),
       impl_latency_takes_priority_(false),
       skip_next_begin_main_frame_to_reduce_latency_(false),
       skip_begin_main_frame_to_reduce_latency_(false),
-      continuous_painting_(false) {
+      continuous_painting_(false),
+      on_battery_power_(false) {
 }
 
 const char* SchedulerStateMachine::OutputSurfaceStateToString(
     OutputSurfaceState state) {
   switch (state) {
     case OUTPUT_SURFACE_ACTIVE:
       return "OUTPUT_SURFACE_ACTIVE";
     case OUTPUT_SURFACE_LOST:
       return "OUTPUT_SURFACE_LOST";
     case OUTPUT_SURFACE_CREATING:
@@ skipping 169 matching lines @@
                     did_create_and_initialize_first_output_surface_);
   state->SetBoolean("impl_latency_takes_priority",
                     impl_latency_takes_priority_);
   state->SetBoolean("main_thread_is_in_high_latency_mode",
                     MainThreadIsInHighLatencyMode());
   state->SetBoolean("skip_begin_main_frame_to_reduce_latency",
                     skip_begin_main_frame_to_reduce_latency_);
   state->SetBoolean("skip_next_begin_main_frame_to_reduce_latency",
                     skip_next_begin_main_frame_to_reduce_latency_);
   state->SetBoolean("continuous_painting", continuous_painting_);
+  state->SetBoolean("on_battery_power", on_battery_power_);
   state->EndDictionary();
 }
 
 void SchedulerStateMachine::AdvanceCurrentFrameNumber() {
   current_frame_number_++;
 
   // "Drain" the ManageTiles funnel.
   if (manage_tiles_funnel_ > 0)
     manage_tiles_funnel_--;
 
@@ skipping 621 matching lines @@
   // don't have a pending tree -- otherwise we should give it a chance to
   // activate.
   // TODO(skyostil): Revisit this when we have more accurate deadline estimates.
   if (commit_state_ == COMMIT_STATE_IDLE && !has_pending_tree_)
     return true;
 
   // Prioritize impl-thread draws in impl_latency_takes_priority_ mode.
   if (impl_latency_takes_priority_)
     return true;
 
+  // If we are on battery power and want to prioritize impl latency because
+  // we don't trust deadline tasks to execute at the right time.
+  if (settings_.prioritize_impl_latency_on_battery && on_battery_power_)

[danakj, 2014/10/09 21:18:02]

i'd say leave on_battery_power_ always false if the setting is off, ie don't set
up the listener when the setting if off.

otherwise you're adding a listener and setting states, but not to use them.

[sunnyps, 2014/10/09 22:04:39]

I agree. I'll rename on_battery_power_ to
impl_latency_takes_priority_on_battery_ so that it's clear that it takes both
the settings flag and power state into account. Also I believe that the name
"on_battery_power" might confuse someone if it doesn't actually reflect the
power state of the system and means something else. 

[danakj, 2014/10/09 22:08:27]

Eh, maybe it's fine to have it just be false when its not known. I don't find
the current name bad at all, but whatever you and the other scheduler folks
perfer :)

+    return true;
+
   return false;
 }
 
 bool SchedulerStateMachine::MainThreadIsInHighLatencyMode() const {
   // If a commit is pending before the previous commit has been drawn, we
   // are definitely in a high latency mode.
   if (CommitPending() && (active_tree_needs_first_draw_ || has_pending_tree_))
     return true;
 
   // If we just sent a BeginMainFrame and haven't hit the deadline yet, the main
@@ skipping 207 matching lines @@
       static_cast<int>(begin_impl_frame_state_),
       static_cast<int>(commit_state_),
       has_pending_tree_ ? 'T' : 'F',
       pending_tree_is_ready_for_activation_ ? 'T' : 'F',
       active_tree_needs_first_draw_ ? 'T' : 'F',
       max_pending_swaps_,
       pending_swaps_);
 }
 
 }  // namespace cc