Reduce CPU usage of download shelf UI. (both MD and pre-MD shelves)

chrome/browser/ui/views/download/download_item_view.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/views/download/download_item_view.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 218 matching lines @@
   // ExperienceSampling: If the user took no action to remove the warning
   // before it disappeared, then the user effectively dismissed the download
   // without keeping it.
   if (sampling_event_.get())
     sampling_event_->CreateUserDecisionEvent(ExperienceSamplingEvent::kIgnore);
 }
 
 // Progress animation handlers.
 
 void DownloadItemView::StartDownloadProgress() {
-  if (progress_timer_.IsRunning())
+  if (progress_start_time_ != base::TimeTicks())
     return;
   progress_start_time_ = base::TimeTicks::Now();
-  progress_timer_.Start(
-      FROM_HERE,
-      base::TimeDelta::FromMilliseconds(DownloadShelf::kProgressRateMs),

[asanka, 2015/12/18 03:39:16]

Would you be willing to get rid of this 30ms timer on Mac as well?

[Evan Stade, 2015/12/18 19:01:38]

yea I meant to look at doing that, thanks for reminding me. I don't have a mac
to verify it doesn't break, though.

[Evan Stade, 2015/12/29 18:50:49]

This seems complicated enough that I'd want someone with an OSX build to have a
look at doing it.

-      base::Bind(&DownloadItemView::SchedulePaint, base::Unretained(this)));
 }
 
 void DownloadItemView::StopDownloadProgress() {
-  if (!progress_timer_.IsRunning())
+  if (progress_start_time_ == base::TimeTicks())
     return;
   previous_progress_elapsed_ += base::TimeTicks::Now() - progress_start_time_;
   progress_start_time_ = base::TimeTicks();
-  progress_timer_.Stop();
 }
 
 void DownloadItemView::OnExtractIconComplete(gfx::Image* icon_bitmap) {
   if (icon_bitmap)
     shelf_->SchedulePaint();
 }
 
 // DownloadObserver interface.
 
 // Update the progress graphic on the icon and our text status label
@@ skipping 13 matching lines @@
     ShowWarningDialog();
     // Force the shelf to layout again as our size has changed.
     shelf_->Layout();
     SchedulePaint();
   } else {
     base::string16 status_text = model_.GetStatusText();
     switch (download()->GetState()) {
       case DownloadItem::IN_PROGRESS:
         download()->IsPaused() ?
             StopDownloadProgress() : StartDownloadProgress();
+        SchedulePaint();
         LoadIconIfItemPathChanged();
         break;
       case DownloadItem::INTERRUPTED:
         StopDownloadProgress();
         complete_animation_.reset(new gfx::SlideAnimation(this));
         complete_animation_->SetSlideDuration(kInterruptedAnimationDurationMs);
         complete_animation_->SetTweenType(gfx::Tween::LINEAR);
         complete_animation_->Show();
         SchedulePaint();
         LoadIcon();
@@ skipping 23 matching lines @@
     status_text_ = status_text;
   }
 
   base::string16 new_tip = model_.GetTooltipText(font_list_, kTooltipMaxWidth);
   if (new_tip != tooltip_text_) {
     tooltip_text_ = new_tip;
     TooltipTextChanged();
   }
 
   UpdateAccessibleName();
-
-  // We use the parent's (DownloadShelfView's) SchedulePaint, since there
-  // are spaces between each DownloadItemView that the parent is responsible
-  // for painting.
-  shelf_->SchedulePaint();
 }
 
 void DownloadItemView::OnDownloadDestroyed(DownloadItem* download) {
   shelf_->RemoveDownloadView(this);  // This will delete us!
 }
 
 void DownloadItemView::OnDownloadOpened(DownloadItem* download) {
   disabled_while_opening_ = true;
   SetEnabled(false);
   base::MessageLoop::current()->task_runner()->PostDelayedTask(
@@ skipping 1044 matching lines @@
 void DownloadItemView::AnimateStateTransition(State from, State to,
                                               gfx::SlideAnimation* animation) {
   if (from == NORMAL && to == HOT) {
     animation->Show();
   } else if (from == HOT && to == NORMAL) {
     animation->Hide();
   } else if (from != to) {
     animation->Reset((to == HOT) ? 1.0 : 0.0);
   }
 }