b=574481; fix layers lifetime issues; part 1 - add API; r=roc

gfx/layers/ImageLayers.h

@@ -172,6 +172,13 @@ public:
    */
   virtual gfxIntSize GetCurrentSize() = 0;
 
+  /**
+   * Set a new layer manager for this image container.  It must be
+   * either of the same type as the container's current layer manager,
+   * or null.  TRUE is returned on success.
+   */
+  virtual PRBool SetLayerManager(LayerManager *aManager) = 0;
+
 protected:
   LayerManager* mManager;
 

gfx/layers/Layers.h

@@ -142,12 +142,21 @@ public:
     LAYERS_D3D9
   };
 
-  LayerManager() : mUserData(nsnull)
+  LayerManager() : mUserData(nsnull), mDestroyed(PR_FALSE)
   {
     InitLog();
   }
   virtual ~LayerManager() {}
 
+  /**
+   * Release layers and resources held by this layer manager, and mark
+   * it as destroyed.  Should do any cleanup necessary in preparation
+   * for its widget going away.  After this call, only user data calls
+   * are valid on the layer manager.
+   */
+  virtual void Destroy() { mDestroyed = PR_TRUE; }
+  PRBool IsDestroyed() { return mDestroyed; }
+
   /**
    * Start a new transaction. Nested transactions are not allowed so
    * there must be no transaction currently in progress.
@@ -297,6 +306,7 @@ public:
 protected:
   nsRefPtr<Layer> mRoot;
   void* mUserData;
+  PRPackedBool mDestroyed;
 
   // Print interesting information about this into aTo.  Internally
   // used to implement Dump*() and Log*().
@@ -328,7 +338,9 @@ public:
   virtual ~Layer() {}
 
   /**
-   * Returns the LayoutManager this Layer belongs to. Cannot be null.
+   * Returns the LayerManager this Layer belongs to. Note that the layer
+   * manager might be in a destroyed state, at which point it's only
+   * valid to set/get user data from it.
    */
   LayerManager* Manager() { return mManager; }
 
@@ -387,6 +399,7 @@ public:
     }
     Mutated();
   }
+
   /**
    * CONSTRUCTION PHASE ONLY
    * Set a clip rect which will be applied to this layer as it is