Support for drawing a debug border around animated layers

cc/layers/layer_impl.h

 // Copyright 2011 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.
 
 #ifndef CC_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <set>
 #include <string>
 
@@ skipping 334 matching lines @@
   void SetBounds(gfx::Size bounds);
   gfx::Size bounds() const { return bounds_; }
 
   void SetContentBounds(gfx::Size content_bounds);
   gfx::Size content_bounds() const { return draw_properties_.content_bounds; }
 
   float contents_scale_x() const { return draw_properties_.contents_scale_x; }
   float contents_scale_y() const { return draw_properties_.contents_scale_y; }
   void SetContentsScale(float contents_scale_x, float contents_scale_y);
 
+  // Computes a box in screen space that should entirely contain the layer's
+  // bounds through the entirety of the layer's current animation. Returns true
+  // on success.

[Ian Vollick, 2013/11/28 00:44:58]

It's not quite success, IIRC. I thought we returned false if the layer was
unaffected by an animation? It returns true whenever we need to inflate bounds
to account for animation, right?

[Ian Vollick, 2013/12/06 20:24:28]

Alex pointed out offline, that although we'll return false when we're not
animated, |box| in that case really won't be correct (I thought it would
previously). The problem is that for |box| to be correct, it would still have to
be transformed into screen space by all the static transforms in the hierarchy,
but we skip this work.

tl;dr - Ignore me :)

[avallee, 2013/12/06 22:08:32]

Tweaked the comment.

+  bool GetAnimationBounds(gfx::BoxF* out) const { return false; }
+
   virtual void CalculateContentsScale(float ideal_contents_scale,
                                       float device_scale_factor,
                                       float page_scale_factor,
                                       bool animating_transform_to_screen,
                                       float* contents_scale_x,
                                       float* contents_scale_y,
                                       gfx::Size* content_bounds);
 
   void SetScrollOffsetDelegate(
       LayerScrollOffsetDelegate* scroll_offset_delegate);
@@ skipping 279 matching lines @@
   // Group of properties that need to be computed based on the layer tree
   // hierarchy before layers can be drawn.
   DrawProperties<LayerImpl> draw_properties_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_