Makes FramePainter not animate the header if the parent (a workspace)

ash/wm/frame_painter.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 "ash/wm/frame_painter.h"
 
 #include "ash/ash_constants.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/window_util.h"
@@ skipping 281 matching lines @@
   return kThemeFrameImageInsetX;
 }
 
 void FramePainter::PaintHeader(views::NonClientFrameView* view,
                                gfx::Canvas* canvas,
                                HeaderMode header_mode,
                                int theme_frame_id,
                                const gfx::ImageSkia* theme_frame_overlay) {
   if (previous_theme_frame_id_ != 0 &&
       previous_theme_frame_id_ != theme_frame_id) {
-    crossfade_animation_.reset(new ui::SlideAnimation(this));
-    crossfade_theme_frame_id_ = previous_theme_frame_id_;
-    crossfade_opacity_ = previous_opacity_;
-    crossfade_animation_->SetSlideDuration(kActivationCrossfadeDurationMs);
-    crossfade_animation_->Show();
+    aura::Window* parent = frame_->GetNativeWindow()->parent();
+    // Don't animate the header if the parent (a workspace) is already
+    // animating. Doing so results in continually painting during the animation
+    // and gives a slower frame rate.
+    // TODO(sky): expose a better way to determine this rather than assuming
+    // the parent is a workspace.
+    bool parent_animating = parent &&
+        (parent->layer()->GetAnimator()->IsAnimatingProperty(
+            ui::LayerAnimationElement::OPACITY) ||
+         parent->layer()->GetAnimator()->IsAnimatingProperty(
+             ui::LayerAnimationElement::VISIBILITY));
+    if (!parent_animating) {
+      crossfade_animation_.reset(new ui::SlideAnimation(this));
+      crossfade_theme_frame_id_ = previous_theme_frame_id_;
+      crossfade_opacity_ = previous_opacity_;
+      crossfade_animation_->SetSlideDuration(kActivationCrossfadeDurationMs);
+      crossfade_animation_->Show();
+    } else {
+      crossfade_animation_.reset();
+    }
   }
 
   int opacity =
       GetHeaderOpacity(header_mode, theme_frame_id, theme_frame_overlay);
   ui::ThemeProvider* theme_provider = frame_->GetThemeProvider();
   gfx::ImageSkia* theme_frame = theme_provider->GetImageSkiaNamed(
       theme_frame_id);
   header_frame_bounds_ = gfx::Rect(0, 0, view->width(), theme_frame->height());
 
   const int kCornerRadius = 2;
@@ skipping 325 matching lines @@
   for (std::set<FramePainter*>::const_iterator it = instances_->begin();
        it != instances_->end();
        ++it) {
     FramePainter* painter = *it;
     if (IsVisibleNormalWindow(painter->window_))
       painter->frame_->non_client_view()->SchedulePaint();
   }
 }
 
 }  // namespace ash