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

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

Index: chrome/browser/ui/views/download/download_item_view_md.cc
diff --git a/chrome/browser/ui/views/download/download_item_view_md.cc b/chrome/browser/ui/views/download/download_item_view_md.cc
index 7df05cfb42edf62d50b806b82006e19b4442e62d..e5fb1fddf98338ce3a1ef6b5f4453a5d87b0ab1e 100644
--- a/chrome/browser/ui/views/download/download_item_view_md.cc
+++ b/chrome/browser/ui/views/download/download_item_view_md.cc
@@ -199,21 +199,16 @@ DownloadItemViewMd::~DownloadItemViewMd() {
 // Progress animation handlers.
 
 void DownloadItemViewMd::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),
-      base::Bind(&DownloadItemViewMd::SchedulePaint, base::Unretained(this)));
 }
 
 void DownloadItemViewMd::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();
 }
 
 // static
@@ -254,6 +249,7 @@ void DownloadItemViewMd::OnDownloadUpdated(DownloadItem* download_item) {
       case DownloadItem::IN_PROGRESS:
         download()->IsPaused() ? StopDownloadProgress()
                                : StartDownloadProgress();
+        SchedulePaint();
         LoadIconIfItemPathChanged();
         break;
       case DownloadItem::INTERRUPTED:
@@ -297,11 +293,6 @@ void DownloadItemViewMd::OnDownloadUpdated(DownloadItem* download_item) {
   }
 
   UpdateAccessibleName();
-
-  // We use the parent's (DownloadShelfView's) SchedulePaint, since there
-  // are spaces between each DownloadItemViewMd that the parent is responsible
-  // for painting.
-  shelf_->SchedulePaint();
 }
 
 void DownloadItemViewMd::OnDownloadDestroyed(DownloadItem* download) {