Remove layout during paint in Tab

chrome/browser/ui/views/tabs/tab.cc

Index: chrome/browser/ui/views/tabs/tab.cc
diff --git a/chrome/browser/ui/views/tabs/tab.cc b/chrome/browser/ui/views/tabs/tab.cc
index 8313719bd8881a6c1db6df5af3d1ee5abd372b52..32a774bfd2da7374ba5d08aacf25c72135a6638c 100644
--- a/chrome/browser/ui/views/tabs/tab.cc
+++ b/chrome/browser/ui/views/tabs/tab.cc
@@ -545,6 +545,9 @@ bool Tab::IsActive() const {
 void Tab::ActiveStateChanged() {
   OnButtonColorMaybeChanged();
   media_indicator_button_->UpdateEnabledForMuteToggle();
+
+  if (ShouldShowCloseBox() != showing_close_button_)

[miu, 2016/01/08 00:25:39]

I think we have to unconditionally call Layout() here.  The reason is that the
tab's active state changes the set of which buttons, favicon, title, etc. are
visible.

For reference, see the three methods starting here:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ui/...

Even if what you have here always results in the correct behavior, it implies
knowledge internal to c/b/ui/tabs/tab_utils.cc.

[enne (OOO), 2016/01/08 01:46:25]

Thanks! Updated the patch.

+    Layout();
 }
 
 bool Tab::IsSelected() const {
@@ -1176,18 +1179,9 @@ void Tab::DataChanged(const TabRendererData& old) {
 }
 
 void Tab::PaintTab(gfx::Canvas* canvas) {
-  // See if the model changes whether the icons should be painted.
-  const bool show_icon = ShouldShowIcon();
-  const bool show_media_indicator = ShouldShowMediaIndicator();
-  const bool show_close_button = ShouldShowCloseBox();
-  if (show_icon != showing_icon_ ||
-      show_media_indicator != showing_media_indicator_ ||
-      show_close_button != showing_close_button_)
-    Layout();
-
   PaintTabBackground(canvas);
 
-  if (show_icon)
+  if (showing_icon_)
     PaintIcon(canvas);
 }