Backed out changeset 703df62e855b due to crashes reported in bug 693086

gfx/layers/basic/BasicLayers.cpp

@@ -532,9 +532,6 @@ public:
     ThebesLayer::ComputeEffectiveTransforms(aTransformToSurface);
   }
 
-  // Sync front/back buffers content
-  virtual void SyncFrontBufferToBackBuffer() {}
-
 protected:
   BasicLayerManager* BasicManager()
   {
@@ -659,7 +656,6 @@ BasicThebesLayer::PaintThebes(gfxContext* aContext,
   if (aReadback && UsedForReadback()) {
     aReadback->GetThebesLayerUpdates(this, &readbackUpdates);
   }
-  SyncFrontBufferToBackBuffer();
 
   bool canUseOpaqueSurface = CanUseOpaqueSurface();
   Buffer::ContentType contentType =
@@ -2158,13 +2154,13 @@ public:
   BasicShadowableThebesLayer(BasicShadowLayerManager* aManager)
     : BasicThebesLayer(aManager)
     , mIsNewBuffer(false)
-    , mFrontAndBackBufferDiffer(false)
   {
     MOZ_COUNT_CTOR(BasicShadowableThebesLayer);
   }
   virtual ~BasicShadowableThebesLayer()
   {
-    DestroyBackBuffer();
+    if (IsSurfaceDescriptorValid(mBackBuffer))
+      BasicManager()->ShadowLayerForwarder::DestroySharedSurface(&mBackBuffer);
     MOZ_COUNT_DTOR(BasicShadowableThebesLayer);
   }
 
@@ -2177,7 +2173,7 @@ public:
   virtual ShadowableLayer* AsShadowableLayer() { return this; }
   virtual bool MustRetainContent() { return HasShadow(); }
 
-  void SetBackBufferAndAttrs(const OptionalThebesBuffer& aBuffer,
+  void SetBackBufferAndAttrs(const ThebesBuffer& aBuffer,
                              const nsIntRegion& aValidRegion,
                              const OptionalThebesBuffer& aReadOnlyFrontBuffer,
                              const nsIntRegion& aFrontUpdatedRegion);
@@ -2190,8 +2186,6 @@ public:
 
   virtual BasicShadowableThebesLayer* AsThebes() { return this; }
 
-  virtual void SyncFrontBufferToBackBuffer();
-
 private:
   BasicShadowLayerManager* BasicManager()
   {
@@ -2210,89 +2204,46 @@ private:
   NS_OVERRIDE virtual already_AddRefed<gfxASurface>
   CreateBuffer(Buffer::ContentType aType, const nsIntSize& aSize);
 
-  void DestroyBackBuffer()
-  {
-    if (IsSurfaceDescriptorValid(mBackBuffer)) {
-      BasicManager()->ShadowLayerForwarder::DestroySharedSurface(&mBackBuffer);
-    }
-  }
-
   // This describes the gfxASurface we hand to mBuffer.  We keep a
   // copy of the descriptor here so that we can call
   // DestroySharedSurface() on the descriptor.
   SurfaceDescriptor mBackBuffer;
-  nsIntRect mBackBufferRect;
-  nsIntPoint mBackBufferRectRotation;
 
   bool mIsNewBuffer;
-  OptionalThebesBuffer mROFrontBuffer;
-  nsIntRegion mFrontUpdatedRegion;
-  nsIntRegion mFrontValidRegion;
-  PRPackedBool mFrontAndBackBufferDiffer;
 };
 
 void
-BasicShadowableThebesLayer::SetBackBufferAndAttrs(const OptionalThebesBuffer& aBuffer,
+BasicShadowableThebesLayer::SetBackBufferAndAttrs(const ThebesBuffer& aBuffer,
                                                   const nsIntRegion& aValidRegion,
                                                   const OptionalThebesBuffer& aReadOnlyFrontBuffer,
                                                   const nsIntRegion& aFrontUpdatedRegion)
 {
-  if (OptionalThebesBuffer::Tnull_t == aBuffer.type()) {
+  mBackBuffer = aBuffer.buffer();
-    mBackBuffer = SurfaceDescriptor();
+  nsRefPtr<gfxASurface> backBuffer = BasicManager()->OpenDescriptor(mBackBuffer);
-  } else {
-    mBackBuffer = aBuffer.get_ThebesBuffer().buffer();
-    mBackBufferRect = aBuffer.get_ThebesBuffer().rect();
-    mBackBufferRectRotation = aBuffer.get_ThebesBuffer().rotation();
-  }
-  mFrontAndBackBufferDiffer = true;
-  mROFrontBuffer = aReadOnlyFrontBuffer;
-  mFrontUpdatedRegion = aFrontUpdatedRegion;
-  mFrontValidRegion = aValidRegion;
-}
 
-void
+  if (OptionalThebesBuffer::Tnull_t == aReadOnlyFrontBuffer.type()) {
-BasicShadowableThebesLayer::SyncFrontBufferToBackBuffer()
-{
-  if (!mFrontAndBackBufferDiffer) {
-    return;
-  }
-
-  nsRefPtr<gfxASurface> backBuffer;
-  if (!IsSurfaceDescriptorValid(mBackBuffer)) {
-    NS_ABORT_IF_FALSE(mROFrontBuffer.type() == OptionalThebesBuffer::TThebesBuffer,
-                      "should have a front RO buffer by now");
-    const ThebesBuffer roFront = mROFrontBuffer.get_ThebesBuffer();
-    nsRefPtr<gfxASurface> roFrontBuffer = BasicManager()->OpenDescriptor(roFront.buffer());
-    backBuffer = CreateBuffer(roFrontBuffer->GetContentType(), roFrontBuffer->GetSize());
-  } else {
-    backBuffer = BasicManager()->OpenDescriptor(mBackBuffer);
-  }
-  mFrontAndBackBufferDiffer = false;
-
-  if (OptionalThebesBuffer::Tnull_t == mROFrontBuffer.type()) {
     // We didn't get back a read-only ref to our old back buffer (the
     // parent's new front buffer).  If the parent is pushing updates
     // to a texture it owns, then we probably got back the same buffer
     // we pushed in the update and all is well.  If not, ...
-    mValidRegion = mFrontValidRegion;
+    mValidRegion = aValidRegion;
-    mBuffer.SetBackingBuffer(backBuffer, mBackBufferRect, mBackBufferRectRotation);
+    mBuffer.SetBackingBuffer(backBuffer, aBuffer.rect(), aBuffer.rotation());
     return;
   }
 
   MOZ_LAYERS_LOG(("BasicShadowableThebes(%p): reading back <x=%d,y=%d,w=%d,h=%d>",
                   this,
-                  mFrontUpdatedRegion.GetBounds().x,
+                  aFrontUpdatedRegion.GetBounds().x,
-                  mFrontUpdatedRegion.GetBounds().y,
+                  aFrontUpdatedRegion.GetBounds().y,
-                  mFrontUpdatedRegion.GetBounds().width,
+                  aFrontUpdatedRegion.GetBounds().width,
-                  mFrontUpdatedRegion.GetBounds().height));
+                  aFrontUpdatedRegion.GetBounds().height));
 
-  const ThebesBuffer roFront = mROFrontBuffer.get_ThebesBuffer();
+  const ThebesBuffer roFront = aReadOnlyFrontBuffer.get_ThebesBuffer();
   nsRefPtr<gfxASurface> roFrontBuffer = BasicManager()->OpenDescriptor(roFront.buffer());
   mBuffer.SetBackingBufferAndUpdateFrom(
     backBuffer,
     roFrontBuffer, roFront.rect(), roFront.rotation(),
-    mFrontUpdatedRegion);
+    aFrontUpdatedRegion);
-  mIsNewBuffer = false;
   // Now the new back buffer has the same (interesting) pixels as the
   // new front buffer, and mValidRegion et al. are correct wrt the new
   // back buffer (i.e. as they were for the old back buffer)
@@ -2354,21 +2305,36 @@ BasicShadowableThebesLayer::CreateBuffer(Buffer::ContentType aType,
                   aSize.width, aSize.height));
 
   if (IsSurfaceDescriptorValid(mBackBuffer)) {
+    BasicManager()->DestroyedThebesBuffer(BasicManager()->Hold(this),
+                                          mBackBuffer);
     mBackBuffer = SurfaceDescriptor();
   }
 
   // XXX error handling
+  SurfaceDescriptor tmpFront;
+  if (BasicManager()->ShouldDoubleBuffer()) {
+    if (!BasicManager()->AllocDoubleBuffer(gfxIntSize(aSize.width, aSize.height),
+                                           aType,
+                                           &tmpFront,
+                                           &mBackBuffer)) {
+      NS_RUNTIMEABORT("creating ThebesLayer 'back buffer' failed!");
+    }
+  } else {
     if (!BasicManager()->AllocBuffer(gfxIntSize(aSize.width, aSize.height),
                                      aType,
                                      &mBackBuffer)) {
       NS_RUNTIMEABORT("creating ThebesLayer 'back buffer' failed!");
     }
+  }
 
   NS_ABORT_IF_FALSE(!mIsNewBuffer,
                     "Bad! Did we create a buffer twice without painting?");
-
   mIsNewBuffer = true;
 
+  BasicManager()->CreatedThebesBuffer(BasicManager()->Hold(this),
+                                      nsIntRegion(),
+                                      nsIntRect(),
+                                      tmpFront);
   return BasicManager()->OpenDescriptor(mBackBuffer);
 }
 
@@ -2715,6 +2681,9 @@ public:
     MOZ_COUNT_DTOR(BasicShadowThebesLayer);
   }
 
+  virtual void SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                              const nsIntRegion& aValidRegion);
+
   virtual void SetValidRegion(const nsIntRegion& aRegion)
   {
     mOldValidRegion = mValidRegion;
@@ -2729,7 +2698,7 @@ public:
 
   virtual void
   Swap(const ThebesBuffer& aNewFront, const nsIntRegion& aUpdatedRegion,
-       OptionalThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
+       ThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
        OptionalThebesBuffer* aReadOnlyFront, nsIntRegion* aFrontUpdatedRegion);
 
   virtual void DestroyFrontBuffer()
@@ -2740,7 +2709,6 @@ public:
 
     if (IsSurfaceDescriptorValid(mFrontBufferDescriptor)) {
       mAllocator->DestroySharedSurface(&mFrontBufferDescriptor);
-      mFrontBufferDescriptor = SurfaceDescriptor();
     }
   }
 
@@ -2765,46 +2733,48 @@ private:
   nsIntRegion mOldValidRegion;
 };
 
+void
+BasicShadowThebesLayer::SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                                       const nsIntRegion& aValidRegion)
+{
+  mValidRegion = mOldValidRegion = aValidRegion;
+
+  NS_ABORT_IF_FALSE(OptionalThebesBuffer::Tnull_t != aNewFront.type(),
+                    "aNewFront must be valid here!");
+
+  const ThebesBuffer newFront = aNewFront.get_ThebesBuffer();
+  nsRefPtr<gfxASurface> newFrontBuffer =
+    BasicManager()->OpenDescriptor(newFront.buffer());
+
+  nsRefPtr<gfxASurface> unused;
+  nsIntRect unusedRect;
+  nsIntPoint unusedRotation;
+  mFrontBuffer.Swap(newFrontBuffer, newFront.rect(), newFront.rotation(),
+                    getter_AddRefs(unused), &unusedRect, &unusedRotation);
+  mFrontBufferDescriptor = newFront.buffer();
+}
+
 void
 BasicShadowThebesLayer::Swap(const ThebesBuffer& aNewFront,
                              const nsIntRegion& aUpdatedRegion,
-                             OptionalThebesBuffer* aNewBack,
+                             ThebesBuffer* aNewBack,
                              nsIntRegion* aNewBackValidRegion,
                              OptionalThebesBuffer* aReadOnlyFront,
                              nsIntRegion* aFrontUpdatedRegion)
 {
-  nsRefPtr<gfxASurface> newFrontBuffer =
-    BasicManager()->OpenDescriptor(aNewFront.buffer());
-
-  if (IsSurfaceDescriptorValid(mFrontBufferDescriptor)) {
-    nsRefPtr<gfxASurface> currentFront = BasicManager()->OpenDescriptor(mFrontBufferDescriptor);
-    if (currentFront->GetSize() != newFrontBuffer->GetSize()) {
-      // Current front buffer is obsolete
-      DestroyFrontBuffer();
-    }
-  }
   // This code relies on Swap() arriving *after* attribute mutations.
-  if (IsSurfaceDescriptorValid(mFrontBufferDescriptor)) {
+  aNewBack->buffer() = mFrontBufferDescriptor;
-    *aNewBack = ThebesBuffer();
-    aNewBack->get_ThebesBuffer().buffer() = mFrontBufferDescriptor;
-  } else {
-    *aNewBack = null_t();
-  }
   // We have to invalidate the pixels painted into the new buffer.
   // They might overlap with our old pixels.
   aNewBackValidRegion->Sub(mOldValidRegion, aUpdatedRegion);
 
+  nsRefPtr<gfxASurface> newFrontBuffer =
+    BasicManager()->OpenDescriptor(aNewFront.buffer());
+
   nsRefPtr<gfxASurface> unused;
-  nsIntRect backRect;
-  nsIntPoint backRotation;
   mFrontBuffer.Swap(
     newFrontBuffer, aNewFront.rect(), aNewFront.rotation(),
-    getter_AddRefs(unused), &backRect, &backRotation);
+    getter_AddRefs(unused), &aNewBack->rect(), &aNewBack->rotation());
-
-  if (aNewBack->type() != OptionalThebesBuffer::Tnull_t) {
-    aNewBack->get_ThebesBuffer().rect() = backRect;
-    aNewBack->get_ThebesBuffer().rotation() = backRotation;
-  }
 
   mFrontBufferDescriptor = aNewFront.buffer();
 

gfx/layers/d3d10/LayerManagerD3D10.cpp

@@ -729,6 +729,11 @@ LayerManagerD3D10::Render()
         windowLayer = new WindowLayer(this);
         windowLayer->SetShadow(ConstructShadowFor(windowLayer));
         CreatedThebesLayer(windowLayer);
+        ShadowLayerForwarder::CreatedThebesBuffer(windowLayer,
+                                                  contentRect,
+                                                  contentRect,
+                                                  SurfaceDescriptor());
+
         mRootForShadowTree->InsertAfter(windowLayer, nsnull);
         ShadowLayerForwarder::InsertAfter(mRootForShadowTree, windowLayer);
     }

gfx/layers/d3d10/ThebesLayerD3D10.cpp

@@ -469,10 +469,18 @@ ShadowThebesLayerD3D10::~ShadowThebesLayerD3D10()
 {
 }
 
+void
+ShadowThebesLayerD3D10::SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                                       const nsIntRegion& aValidRegion)
+{
+  NS_ABORT_IF_FALSE(OptionalThebesBuffer::Tnull_t == aNewFront.type(),
+                    "Expected dummy front buffer initially");
+}
+
 void
 ShadowThebesLayerD3D10::Swap(
   const ThebesBuffer& aNewFront, const nsIntRegion& aUpdatedRegion,
-  OptionalThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
+  ThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
   OptionalThebesBuffer* aReadOnlyFront, nsIntRegion* aFrontUpdatedRegion)
 {
   nsRefPtr<ID3D10Texture2D> newBackBuffer = mTexture;
@@ -482,7 +490,7 @@ ShadowThebesLayerD3D10::Swap(
 
   // The content process tracks back/front buffers on its own, so
   // the newBack is in essence unused.
-  aNewBack->get_ThebesBuffer().buffer() = aNewFront.buffer();
+  aNewBack->buffer() = aNewFront.buffer();
 
   // The content process doesn't need to read back from the front
   // buffer (yet).

gfx/layers/d3d10/ThebesLayerD3D10.h

@@ -108,9 +108,12 @@ public:
   ShadowThebesLayerD3D10(LayerManagerD3D10* aManager);
   virtual ~ShadowThebesLayerD3D10();
 
+  // ShadowThebesLayer impl
+  virtual void SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                              const nsIntRegion& aValidRegion);
   virtual void
   Swap(const ThebesBuffer& aNewFront, const nsIntRegion& aUpdatedRegion,
-       OptionalThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
+       ThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
        OptionalThebesBuffer* aReadOnlyFront, nsIntRegion* aFrontUpdatedRegion);
   virtual void DestroyFrontBuffer();
 

gfx/layers/d3d9/ThebesLayerD3D9.cpp

@@ -619,17 +619,25 @@ ShadowThebesLayerD3D9::~ShadowThebesLayerD3D9()
 {}
 
 void
-ShadowThebesLayerD3D9::Swap(const ThebesBuffer& aNewFront,
+ShadowThebesLayerD3D9::SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
-                           const nsIntRegion& aUpdatedRegion,
+                                     const nsIntRegion& aValidRegion)
-                           OptionalThebesBuffer* aNewBack,
-                           nsIntRegion* aNewBackValidRegion,
-                           OptionalThebesBuffer* aReadOnlyFront,
-                           nsIntRegion* aFrontUpdatedRegion)
 {
   if (!mBuffer) {
     mBuffer = new ShadowBufferD3D9(this);
   }
 
+  NS_ASSERTION(OptionalThebesBuffer::Tnull_t == aNewFront.type(),
+               "Only one system-memory buffer expected");
+}
+
+void
+ShadowThebesLayerD3D9::Swap(const ThebesBuffer& aNewFront,
+                           const nsIntRegion& aUpdatedRegion,
+                           ThebesBuffer* aNewBack,
+                           nsIntRegion* aNewBackValidRegion,
+                           OptionalThebesBuffer* aReadOnlyFront,
+                           nsIntRegion* aFrontUpdatedRegion)
+{
   if (mBuffer) {
     nsRefPtr<gfxASurface> surf = ShadowLayerForwarder::OpenDescriptor(aNewFront.buffer());
     mBuffer->Upload(surf, GetVisibleRegion().GetBounds());

gfx/layers/d3d9/ThebesLayerD3D9.h

@@ -120,9 +120,12 @@ public:
   ShadowThebesLayerD3D9(LayerManagerD3D9 *aManager);
   virtual ~ShadowThebesLayerD3D9();
 
+  // ShadowThebesLayer impl
+  virtual void SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                              const nsIntRegion& aValidRegion);
   virtual void
   Swap(const ThebesBuffer& aNewFront, const nsIntRegion& aUpdatedRegion,
-       OptionalThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
+       ThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
        OptionalThebesBuffer* aReadOnlyFront, nsIntRegion* aFrontUpdatedRegion);
   virtual void DestroyFrontBuffer();
 

gfx/layers/ipc/PLayers.ipdl

@@ -109,6 +109,17 @@ union CanvasSurface {
   null_t;
 };
 
+// For the "buffer creation" operations, we send an initial front
+// buffer that only contains (transparent) black pixels just so that
+// we can swap it back after the first OpPaint without a special case.
+
+struct OpCreateThebesBuffer {
+  PLayer layer;
+  OptionalThebesBuffer initialFront;
+  nsIntRegion frontValidRegion;
+};
+struct OpDestroyThebesFrontBuffer { PLayer layer; };
+
 // Change a layer's attributes
 struct CommonLayerAttributes {
   nsIntRegion visibleRegion;
@@ -183,6 +194,8 @@ union Edit {
   OpCreateImageLayer;
   OpCreateColorLayer;
   OpCreateCanvasLayer;
+  OpCreateThebesBuffer;
+  OpDestroyThebesFrontBuffer;
 
   OpSetLayerAttributes;
 
@@ -204,7 +217,7 @@ struct OpImageSwap { PLayer layer; SharedImage newBackImage; };
 
 struct OpThebesBufferSwap {
   PLayer layer;
-  OptionalThebesBuffer newBackBuffer;
+  ThebesBuffer newBackBuffer;
   nsIntRegion newValidRegion;
   // If the parent took the child's old back buffer and returned its
   // old front buffer, |readOnlyFrontBuffer| may (if non-null) contain

gfx/layers/ipc/ShadowLayers.cpp

@@ -184,6 +184,31 @@ ShadowLayerForwarder::CreatedCanvasLayer(ShadowableLayer* aCanvas)
   CreatedLayer<OpCreateCanvasLayer>(mTxn, aCanvas);
 }
 
+void
+ShadowLayerForwarder::CreatedThebesBuffer(ShadowableLayer* aThebes,
+                                          const nsIntRegion& aFrontValidRegion,
+                                          const nsIntRect& aBufferRect,
+                                          const SurfaceDescriptor& aTempFrontBuffer)
+{
+  OptionalThebesBuffer buffer = null_t();
+  if (IsSurfaceDescriptorValid(aTempFrontBuffer)) {
+    buffer = ThebesBuffer(aTempFrontBuffer,
+                          aBufferRect,
+                          nsIntPoint(0, 0));
+  }
+  mTxn->AddEdit(OpCreateThebesBuffer(NULL, Shadow(aThebes),
+                                     buffer,
+                                     aFrontValidRegion));
+}
+
+void
+ShadowLayerForwarder::DestroyedThebesBuffer(ShadowableLayer* aThebes,
+                                            const SurfaceDescriptor& aBackBufferToDestroy)
+{
+  mTxn->AddEdit(OpDestroyThebesFrontBuffer(NULL, Shadow(aThebes)));
+  mTxn->AddBufferToDestroy(aBackBufferToDestroy);
+}
+
 void
 ShadowLayerForwarder::Mutated(ShadowableLayer* aMutant)
 {

gfx/layers/ipc/ShadowLayers.h

@@ -140,6 +140,38 @@ public:
   void CreatedColorLayer(ShadowableLayer* aColor);
   void CreatedCanvasLayer(ShadowableLayer* aCanvas);
 
+  /**
+   * Notify the shadow manager that a buffer has been created for the
+   * specificed layer.  |aInitialFrontSurface| is one of the newly
+   * created, transparent black buffers for the layer; the "real"
+   * layer holds on to the other as its back buffer.  We send it
+   * across on buffer creation to avoid special cases in the buffer
+   * swapping logic for Painted*() operations.
+   *
+   * It is expected that Created*Buffer() will be followed by a
+   * Painted*Buffer() in the same transaction, so that
+   * |aInitialFrontBuffer| is never actually drawn to screen.  It is
+   * OK if it is drawn though.
+   */
+  /**
+   * |aBufferRect| is the screen rect covered by |aInitialFrontBuffer|.
+   */
+  void CreatedThebesBuffer(ShadowableLayer* aThebes,
+                           const nsIntRegion& aFrontValidRegion,
+                           const nsIntRect& aBufferRect,
+                           const SurfaceDescriptor& aInitialFrontBuffer);
+
+  /**
+   * The specified layer is destroying its buffers.
+   * |aBackBufferToDestroy| is deallocated when this transaction is
+   * posted to the parent.  During the parent-side transaction, the
+   * shadow is told to destroy its front buffer.  This can happen when
+   * a new front/back buffer pair have been created because of a layer
+   * resize, e.g.
+   */
+  void DestroyedThebesBuffer(ShadowableLayer* aThebes,
+                             const SurfaceDescriptor& aBackBufferToDestroy);
+
   /**
    * At least one attribute of |aMutant| has changed, and |aMutant|
    * needs to sync to its shadow layer.  This initial implementation
@@ -474,6 +506,15 @@ class ShadowThebesLayer : public ShadowLayer,
                           public ThebesLayer
 {
 public:
+  /**
+   * CONSTRUCTION PHASE ONLY
+   *
+   * Override the front buffer and its valid region with the specified
+   * values.  This is called when a new buffer has been created.
+   */
+  virtual void SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                              const nsIntRegion& aValidRegion) = 0;
+
   virtual void InvalidateRegion(const nsIntRegion& aRegion)
   {
     NS_RUNTIMEABORT("ShadowThebesLayers can't fill invalidated regions");
@@ -497,7 +538,7 @@ public:
    */
   virtual void
   Swap(const ThebesBuffer& aNewFront, const nsIntRegion& aUpdatedRegion,
-       OptionalThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
+       ThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
        OptionalThebesBuffer* aReadOnlyFront, nsIntRegion* aFrontUpdatedRegion) = 0;
 
   /**

gfx/layers/ipc/ShadowLayersParent.cpp

@@ -203,7 +203,29 @@ ShadowLayersParent::RecvUpdate(const InfallibleTArray<Edit>& cset,
       AsShadowLayer(edit.get_OpCreateCanvasLayer())->Bind(layer);
       break;
     }
+    case Edit::TOpCreateThebesBuffer: {
+      MOZ_LAYERS_LOG(("[ParentSide] CreateThebesBuffer"));
 
+      const OpCreateThebesBuffer& otb = edit.get_OpCreateThebesBuffer();
+      ShadowThebesLayer* thebes = static_cast<ShadowThebesLayer*>(
+        AsShadowLayer(otb)->AsLayer());
+
+      thebes->SetFrontBuffer(otb.initialFront(), otb.frontValidRegion());
+
+      break;
+    }
+    case Edit::TOpDestroyThebesFrontBuffer: {
+      MOZ_LAYERS_LOG(("[ParentSide] DestroyThebesFrontBuffer"));
+
+      const OpDestroyThebesFrontBuffer& odfb =
+        edit.get_OpDestroyThebesFrontBuffer();
+      ShadowThebesLayer* thebes = static_cast<ShadowThebesLayer*>(
+        AsShadowLayer(odfb)->AsLayer());
+
+      thebes->DestroyFrontBuffer();
+
+      break;
+    }
       // Attributes
     case Edit::TOpSetLayerAttributes: {
       MOZ_LAYERS_LOG(("[ParentSide] SetLayerAttributes"));
@@ -317,7 +339,7 @@ ShadowLayersParent::RecvUpdate(const InfallibleTArray<Edit>& cset,
         static_cast<ShadowThebesLayer*>(shadow->AsLayer());
       const ThebesBuffer& newFront = op.newFrontBuffer();
 
-      OptionalThebesBuffer newBack;
+      ThebesBuffer newBack;
       nsIntRegion newValidRegion;
       OptionalThebesBuffer readonlyFront;
       nsIntRegion frontUpdatedRegion;

gfx/layers/opengl/ThebesLayerOGL.cpp

@@ -878,18 +878,31 @@ ShadowThebesLayerOGL::ShadowThebesLayerOGL(LayerManagerOGL *aManager)
 ShadowThebesLayerOGL::~ShadowThebesLayerOGL()
 {}
 
+void
+ShadowThebesLayerOGL::SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                                     const nsIntRegion& aValidRegion)
+{
+  if (mDestroyed) {
+    return;
+  }
+
+  if (!mBuffer) {
+    mBuffer = new ShadowBufferOGL(this);
+  }
+
+  NS_ASSERTION(OptionalThebesBuffer::Tnull_t == aNewFront.type(),
+               "Only one system-memory buffer expected");
+}
+
 void
 ShadowThebesLayerOGL::Swap(const ThebesBuffer& aNewFront,
                            const nsIntRegion& aUpdatedRegion,
-                           OptionalThebesBuffer* aNewBack,
+                           ThebesBuffer* aNewBack,
                            nsIntRegion* aNewBackValidRegion,
                            OptionalThebesBuffer* aReadOnlyFront,
                            nsIntRegion* aFrontUpdatedRegion)
 {
-  if (!mDestroyed) {
+  if (!mDestroyed && mBuffer) {
-    if (!mBuffer) {
-      mBuffer = new ShadowBufferOGL(this);
-    }
     nsRefPtr<gfxASurface> surf = ShadowLayerForwarder::OpenDescriptor(aNewFront.buffer());
     mBuffer->Upload(surf, aUpdatedRegion, aNewFront.rect(), aNewFront.rotation());
   }

gfx/layers/opengl/ThebesLayerOGL.h

@@ -91,9 +91,12 @@ public:
   ShadowThebesLayerOGL(LayerManagerOGL *aManager);
   virtual ~ShadowThebesLayerOGL();
 
+  // ShadowThebesLayer impl
+  virtual void SetFrontBuffer(const OptionalThebesBuffer& aNewFront,
+                              const nsIntRegion& aValidRegion);
   virtual void
   Swap(const ThebesBuffer& aNewFront, const nsIntRegion& aUpdatedRegion,
-       OptionalThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
+       ThebesBuffer* aNewBack, nsIntRegion* aNewBackValidRegion,
        OptionalThebesBuffer* aReadOnlyFront, nsIntRegion* aFrontUpdatedRegion);
   virtual void DestroyFrontBuffer();