ui: Make compositor unittests access the canvas through PaintRecorder.

ui/compositor/paint_context.h

 // Copyright 2015 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 UI_COMPOSITOR_PAINT_CONTEXT_H_
 #define UI_COMPOSITOR_PAINT_CONTEXT_H_
 
 #include "base/logging.h"
 #include "ui/gfx/geometry/rect.h"
 
@@ skipping 49 matching lines @@
 
 #if DCHECK_IS_ON()
   void Visited(void* visited) const {
     if (!root_visited_)
       root_visited_ = visited;
   }
   void* RootVisited() const { return root_visited_; }
   const gfx::Vector2d& PaintOffset() const { return offset_; }
 #endif
 
+  const gfx::Rect& InvalidationForTesting() const { return invalidation_; }

[sadrul, 2015/04/07 19:05:12]

In a number of components, we expose such things through a TestApi (grep for
TestApi in //ui/) instead of *ForTesting() methods to avoid misuse/accidental
use of test-apis in real code.

[danakj, 2015/04/07 20:09:35]

FWIW Presubmit makes an error if you use a method named ForTesting in a non-test
file.

I wanted to subclass but then I'd have to inject a testing PaintContext into
ui::Layer. I guess a friend class would work too, hm. That's slightly nicer as
it keeps more code/api out of prod. But it also moves access to private things
somewhere else, hm hm.

I think I'll go with it as this for now.. but I wanna think about this TestAPI
idea, thanks for pointing it out.

+
  private:
   // The PaintRecorder needs access to the internal canvas and friends, but we
   // don't want to expose them on this class so that people must go through the
   // recorder to access them.
   friend class PaintRecorder;
 
   // Clone a PaintContext with an additional |offset|.
   PaintContext(const PaintContext& other, const gfx::Vector2d& offset)
       : canvas_(other.canvas_),
         invalidation_(other.invalidation_),
@@ skipping 14 matching lines @@
 #if DCHECK_IS_ON()
   // Used to verify that the |invalidation_| is only used to compare against
   // rects in the same space.
   mutable void* root_visited_;
 #endif
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_PAINT_CONTEXT_H_