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 1fbd1304bc0bf058f54d7b44eed775fc87507d40..1ed2c606a8f339b05dd3e9d506c432b83b7bcfc4 100644
--- a/chrome/browser/ui/views/download/download_item_view_md.cc
+++ b/chrome/browser/ui/views/download/download_item_view_md.cc
@@ -205,10 +205,10 @@ void DownloadItemViewMd::StartDownloadProgress() {
   if (progress_timer_.IsRunning())
     return;
   progress_start_time_ = base::TimeTicks::Now();
-  progress_timer_.Start(
-      FROM_HERE,
-      base::TimeDelta::FromMilliseconds(DownloadShelf::kProgressRateMs),
-      base::Bind(&DownloadItemViewMd::SchedulePaint, base::Unretained(this)));
+  progress_timer_.Start(FROM_HERE, base::TimeDelta::FromMilliseconds(
+                                       DownloadShelf::kProgressRateMs),
+                        base::Bind(&DownloadItemViewMd::ProgressTimerFired,
+                                   base::Unretained(this)));
 }
 
 void DownloadItemViewMd::StopDownloadProgress() {
@@ -257,6 +257,7 @@ void DownloadItemViewMd::OnDownloadUpdated(DownloadItem* download_item) {
       case DownloadItem::IN_PROGRESS:
         download()->IsPaused() ? StopDownloadProgress()
                                : StartDownloadProgress();
+        SchedulePaint();
         LoadIconIfItemPathChanged();
         break;
       case DownloadItem::INTERRUPTED:
@@ -300,11 +301,6 @@ 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) {
@@ -1075,6 +1071,13 @@ void DownloadItemViewMd::AnimateStateTransition(
   }
 }
 
+void DownloadItemViewMd::ProgressTimerFired() {
+  // Only repaint for the indeterminate size case. Otherwise, we'll repaint only
+  // when there's an update notified via OnDownloadUpdated().
+  if (model_.PercentComplete() < 0)
+    SchedulePaint();
+}
+
 SkColor DownloadItemViewMd::GetTextColor() {
   return GetTextColorForThemeProvider(GetThemeProvider());
 }