Changes subtreeShouldRenderToSeparateSurface logic to account for explicit clipping

cc/draw_properties.h

 // Copyright 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.
 
 #ifndef CC_DRAW_PROPERTIES_H_
 #define CC_DRAW_PROPERTIES_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/transform.h"
@@ skipping 37 matching lines @@
     bool screen_space_opacity_is_animating;
     bool target_space_transform_is_animating;
     bool screen_space_transform_is_animating;
 
     // True if the layer can use LCD text.
     bool can_use_lcd_text;
 
     // True if the layer needs to be clipped by clipRect.
     bool is_clipped;
 
+    // True if all chilren can clip to this layer (if is_clipped is true)
+    bool all_children_can_clip;

[shawnsingh, 2012/12/14 07:34:44]

We should definitely add another line to the DrawProperties constructor defined
above, to initialize this correctly.

[whunt, 2012/12/14 18:17:01]

I'm happy to do this but I object to the word "definitely".  This value is
always initialized in the pre-walk before it is used.  If it's not initialized
there it's pretty meaningless.  Also we've already defined it to be meaningless
if is_clipped is false, which is set by default.  Also, it's not clear what the
correct default value should be.  I can set it to false but again, that's not
really any more meaningful than undefined.

On 2012/12/14 07:34:44, shawnsingh wrote:

+
     // The layer whose coordinate space this layer draws into. This can be
     // either the same layer (m_drawProperties.render_target == this) or an
     // ancestor of this layer.
     LayerType* render_target;
 
     // The surface that this layer and its subtree would contribute to.
     scoped_ptr<RenderSurfaceType> render_surface;
 
     // This rect is in the layer's content space.
     gfx::Rect visible_content_rect;
 
     // In target surface space, the rect that encloses the clipped, drawable
     // content of the layer.
     gfx::Rect drawable_content_rect;
 
     // In target surface space, the original rect that clipped this
     // layer. This value is used to avoid unnecessarily changing GL scissor
     // state.
     gfx::Rect clip_rect;
 
     // Does not include this layer itself, only its children and descendants.
     int num_descendants_that_draw_content;
 };
 
 }  // namespace cc
 
 #endif  // CC_DRAW_PROPERTIES_H_