exo: Recreate Surface resources on context lost.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index a6245dae5afdc34756adb3b416c6415d3503bd12..a703d61cac1ff24a264aef01f0ec043e4535807f 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -69,11 +69,25 @@ class Texture;
 
 const int kCompositorLockTimeoutMs = 67;
 
+class COMPOSITOR_EXPORT ContextFactoryObserver {
+ public:
+  virtual ~ContextFactoryObserver() {}
+
+  // Notifies that the ContextProvider returned from
+  // ui::ContextFactory::SharedMainThreadContextProvider was lost.  When this
+  // is called, the old resources (e.g. shared context, GL helper) still
+  // exist, but are about to be destroyed. Getting a reference to those
+  // resources from the ContextFactory (e.g. through
+  // SharedMainThreadContextProvider()) will return newly recreated, valid
+  // resources.
+  virtual void OnLostResources() = 0;
+};
+
 // This class abstracts the creation of the 3D context for the compositor. It is
 // a global object.
 class COMPOSITOR_EXPORT ContextFactory {
  public:
-  virtual ~ContextFactory() {}
+  virtual ~ContextFactory();
 
   // Creates an output surface for the given compositor. The factory may keep
   // per-compositor data (e.g. a shared context), that needs to be cleaned up
@@ -128,6 +142,14 @@ class COMPOSITOR_EXPORT ContextFactory {
                                              base::TimeDelta interval) = 0;
 
   virtual void SetOutputIsSecure(Compositor* compositor, bool secure) = 0;
+
+  void AddObserver(ContextFactoryObserver* observer);
+
+  void RemoveObserver(ContextFactoryObserver* observer);
+
+ protected:
+  ContextFactory();
+  base::ObserverList<ContextFactoryObserver> observer_list_;

[piman, 2016/06/21 01:14:13]

Can we keep this class pure virtual? I realize you're trying to save code, but
because we need multiple inheritance, we should stick to pure interfaces.

 };
 
 // This class represents a lock on the compositor, that can be used to prevent