exo: Add support for subcompositor interface.

components/exo/surface.h

Index: components/exo/surface.h
diff --git a/components/exo/surface.h b/components/exo/surface.h
index 4db760ee667bd9d554ec78335cc3e0cbf1c34d67..0bb6b98b383070bb14fbce39c196ff9ab503ab99 100644
--- a/components/exo/surface.h
+++ b/components/exo/surface.h
@@ -6,10 +6,12 @@
 #define COMPONENTS_EXO_SURFACE_H_
 
 #include <list>
+#include <utility>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/compositor/compositor_observer.h"
 #include "ui/gfx/geometry/rect.h"
@@ -24,6 +26,7 @@ class TracedValue;
 namespace exo {
 class Buffer;
 class SurfaceDelegate;
+class SurfaceObserver;
 
 // This class represents a rectangular area that is displayed on the screen.
 // It has a location, size and pixel contents.
@@ -49,14 +52,40 @@ class Surface : public views::View, public ui::CompositorObserver {
   // This sets the region of the surface that contains opaque content.
   void SetOpaqueRegion(const SkRegion& region);
 
+  // Functions that control sub-surface state. All sub-surface state is
+  // double-buffered and will be applied when Commit() is called.
+  void AddSubSurface(Surface* sub_surface);
+  void RemoveSubSurface(Surface* sub_surface);
+  void SetSubSurfacePosition(Surface* sub_surface, const gfx::Point& position);
+  void PlaceSubSurfaceAbove(Surface* sub_surface, Surface* reference);
+  void PlaceSubSurfaceBelow(Surface* sub_surface, Surface* sibling);
+
   // Surface state (damage regions, attached buffers, etc.) is double-buffered.
   // A Commit() call atomically applies all pending state, replacing the
-  // current state.
+  // current state. Commit() is not guaranteed to be synchronous. See
+  // CommitSurfaceHierarchy() below.
   void Commit();
 
+  // This will synchronously commit all pending state of the surface and its
+  // descendants by recursively calling CommitSurfaceHierarchy() for each
+  // sub-surface with pending state.
+  void CommitSurfaceHierarchy();
+
+  // Returns true if surface is in synchronized mode.
+  bool IsSynchronized() const;
+
   // Set the surface delegate.
   void SetSurfaceDelegate(SurfaceDelegate* delegate);
 
+  // Returns true if surface has been assigned a surface delegate.
+  bool HasSurfaceDelegate() const;
+
+  // Surface does not own observers. It is the responsibility of the observer
+  // to remove itself when it is done observing.
+  void AddSurfaceObserver(SurfaceObserver* observer);
+  void RemoveSurfaceObserver(SurfaceObserver* observer);
+  bool HasSurfaceObserver(const SurfaceObserver* observer) const;
+
   // Returns a trace value representing the state of the surface.
   scoped_refptr<base::trace_event::TracedValue> AsTracedValue() const;
 
@@ -75,6 +104,12 @@ class Surface : public views::View, public ui::CompositorObserver {
   void OnCompositingShuttingDown(ui::Compositor* compositor) override;
 
  private:
+  bool needs_commit_surface_hierarchy() const {
+    return needs_commit_surface_hierarchy_;
+  }
+
+  bool has_contents() const { return has_contents_; }
+
   // The buffer that will become the content of surface when Commit() is called.
   base::WeakPtr<Buffer> pending_buffer_;
 
@@ -96,6 +131,20 @@ class Surface : public views::View, public ui::CompositorObserver {
   // The opaque region to take effect when Commit() is called.
   SkRegion pending_opaque_region_;
 
+  // The stack of sub-surfaces to take effect when Commit() is called.
+  // Bottom-most sub-surface at the front of the list and top-most sub-surface
+  // at the back.
+  using SubSurfaceEntry = std::pair<Surface*, gfx::Point>;
+  using SubSurfaceEntryList = std::list<SubSurfaceEntry>;
+  SubSurfaceEntryList pending_sub_surfaces_;
+
+  // This is true if a call to Commit() as been made but
+  // CommitSurfaceHierarchy() has not yet been called.
+  bool needs_commit_surface_hierarchy_;
+
+  // This is true when surface has some contents assigned to it.
+  bool has_contents_;
+
   // The compsitor being observer or null if not observing a compositor.
   ui::Compositor* compositor_;
 
@@ -104,6 +153,9 @@ class Surface : public views::View, public ui::CompositorObserver {
   // maintains.
   SurfaceDelegate* delegate_;
 
+  // Surface observer list. Surface does not own the observers.
+  base::ObserverList<SurfaceObserver, true> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(Surface);
 };