cc: Use maximum tiling contents scales for picture layer scale

cc/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_LAYER_IMPL_H_
 #define CC_LAYER_IMPL_H_
 
 #include <string>
 
 #include "base/logging.h"
@@ skipping 180 matching lines @@
     void setBounds(const gfx::Size&);
     const gfx::Size& bounds() const { return m_bounds; }
 
     void setContentBounds(const gfx::Size&);
     gfx::Size contentBounds() const { return m_drawProperties.content_bounds; }
 
     float contentsScaleX() const { return m_drawProperties.contents_scale_x; }
     float contentsScaleY() const { return m_drawProperties.contents_scale_y; }
     void setContentsScale(float contentsScaleX, float contentsScaleY);
 
+    virtual void calculateContentsScale(

[danakj, 2013/01/07 15:57:44]

So, this never actually sets the return values on the impl side right? The
float* and gfx::Size* will always be untouched in the current versions of this
method.

Should we add a comment saying that the draw properties are already set on impl
by push properties, and this is just to inform the layers about the ideal
contents scale?

Is it worth having these pointers here that could let a layer override the
contents scale/bounds on impl and not match the main thread (and also not match
any data from the main thread)?

What's your thinking long-term here?

[enne (OOO), 2013/01/07 17:00:01]

The whole point of this function is so that a (Picture)LayerImpl can override
the values from the main thread.  This is my long-term thinking at the moment.

You are correct that most layers get their values from push properties and don't
have any need or ability to change their content bounds or content scale.

PTAL at the newest version.  I added a comment and set the out parameters to the
draw properties themselves to make it clearer.

+        float idealContentsScale,
+        float* contentsScaleX,
+        float* contentsScaleY,
+        gfx::Size* contentBounds) { }
+
     gfx::Vector2d scrollOffset() const { return m_scrollOffset; }
     void setScrollOffset(gfx::Vector2d);
 
     gfx::Vector2d maxScrollOffset() const {return m_maxScrollOffset; }
     void setMaxScrollOffset(gfx::Vector2d);
 
     const gfx::Vector2dF& scrollDelta() const { return m_scrollDelta; }
     void setScrollDelta(const gfx::Vector2dF&);
 
     const gfx::Transform& implTransform() const { return m_implTransform; }
@@ skipping 187 matching lines @@
     // Group of properties that need to be computed based on the layer tree
     // hierarchy before layers can be drawn.
     DrawProperties<LayerImpl, RenderSurfaceImpl> m_drawProperties;
 
     DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }
 
 #endif  // CC_LAYER_IMPL_H_