Remove layout during paint in Tab

chrome/browser/ui/views/tabs/tab.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/tabs/tab.h"
 
 #include <stddef.h>
 #include <limits>
 #include <utility>
 
@@ skipping 527 matching lines @@
   hover_controller_.SetAnimationContainer(container);
 }
 
 bool Tab::IsActive() const {
   return controller_->IsActiveTab(this);
 }
 
 void Tab::ActiveStateChanged() {
   OnButtonColorMaybeChanged();
   media_indicator_button_->UpdateEnabledForMuteToggle();
+  Layout();

[sky, 2016/01/08 16:40:32]

Can we call layout only if we actually need to?

[enne (OOO), 2016/01/08 18:22:27]

Can you and miu sort out what you want to do here? Patch 1 had a conditional
here, but miu didn't want it.

 }
 
 bool Tab::IsSelected() const {
   return controller_->IsTabSelected(this);
 }
 
 void Tab::SetData(const TabRendererData& data) {
   DCHECK(GetWidget());
 
   if (data_.Equals(data))
@@ skipping 611 matching lines @@
   if (data().blocked == old.blocked)
     return;
 
   if (data().blocked)
     StartPulse();
   else
     StopPulse();
 }
 
 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);
 }
 
 void Tab::PaintImmersiveTab(gfx::Canvas* canvas) {
   // Use transparency for the draw-attention animation.
   int alpha = 255;
   if (pulse_animation_ && pulse_animation_->is_animating() && !data().pinned) {
     alpha = pulse_animation_->CurrentValueBetween(
         255, static_cast<int>(255 * kImmersiveTabMinThrobOpacity));
   }
@@ skipping 564 matching lines @@
                          const gfx::ImageSkia& image) {
   DCHECK_NE(scale_factor, ui::SCALE_FACTOR_NONE);
   ImageCacheEntry entry;
   entry.resource_id = resource_id;
   entry.scale_factor = scale_factor;
   entry.image = image;
   image_cache_->push_front(entry);
   if (image_cache_->size() > kMaxImageCacheSize)
     image_cache_->pop_back();
 }