exo: Only create new SurfaceLayer if layer properties change.

components/exo/surface.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 COMPONENTS_EXO_SURFACE_H_
 #define COMPONENTS_EXO_SURFACE_H_
 
 #include <list>
 #include <memory>
 #include <set>
@@ skipping 201 matching lines @@
   void OnCompositingDidCommit(ui::Compositor* compositor) override;
   void OnCompositingStarted(ui::Compositor* compositor,
                             base::TimeTicks start_time) override;
   void OnCompositingEnded(ui::Compositor* compositor) override;
   void OnCompositingAborted(ui::Compositor* compositor) override;
   void OnCompositingLockStateChanged(ui::Compositor* compositor) override {}
   void OnCompositingShuttingDown(ui::Compositor* compositor) override;
 
   void WillDraw(cc::SurfaceId surface_id);
 
+  // Check whether this Surface and its children need to create new cc::Surface
+  // IDs for their contents next time they get new buffer contents.
+  void CheckForCommittingToNewSurface();
+
  private:
   bool needs_commit_surface_hierarchy() const {
     return needs_commit_surface_hierarchy_;
   }
 
+  // Returns true if any child surface needs a commit and has
+  // modified_layer_info_ true.
+  bool HaveChildLayersChanged();
+
+  // Sets that all children must create new cc::SurfaceIds for their contents.
+  void SetChildrenCommitToNewSurface();
+
   // Commit the current attached buffer to a TextureLayer.
   void CommitTextureContents();
 
   // Commit the current attached buffer to a SurfaceLayer.
   void CommitSurfaceContents();
 
   // Set TextureLayer contents to the current buffer.
   void SetTextureLayerContents(ui::Layer* layer);
 
   // Set SurfaceLayer contents to the current buffer.
   void SetSurfaceLayerContents(ui::Layer* layer);
 
   // This returns true when the surface has some contents assigned to it.
   bool has_contents() const { return !!current_buffer_; }
 
   // This is true if the buffer contents should be put in a SurfaceLayer
   // rather than a TextureLayer.
   static bool use_surface_layer_;
 
+  // This is true if it's possible that the layer properties (size, opacity,
+  // etc.) may have been modified since the last commit. Attaching a new
+  // buffer with the same size as the old shouldn't set this to true.
+  bool modified_layer_info_ = true;
+
+  // This is true if the next commit to this surface should put its contents
+  // into a new cc::SurfaceId. This allows for synchronization between Surface
+  // and layer changes.
+  bool commit_to_new_surface_ = true;
+

[reveman, 2016/06/09 14:19:29]

Check my comments in the .cc file but I'm curious to know if this additional
state can't be avoided using some better integration with
CommitSurfaceHierarchy().

   // This is true when Attach() has been called and new contents should take
   // effect next time Commit() is called.
   bool has_pending_contents_;
 
   // The buffer that will become the content of surface when Commit() is called.
   base::WeakPtr<Buffer> pending_buffer_;
 
   cc::SurfaceManager* surface_manager_;
 
   scoped_refptr<SurfaceFactoryOwner> factory_owner_;
@@ skipping 94 matching lines @@
 
   // Surface observer list. Surface does not own the observers.
   base::ObserverList<SurfaceObserver, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(Surface);
 };
 
 }  // namespace exo
 
 #endif  // COMPONENTS_EXO_SURFACE_H_