Bug 539356 - Handled scrolled inactive layers trees correctly. r=roc

gfx/layers/LayerTreeInvalidation.cpp

@@ -91,6 +91,8 @@ struct LayerPropertiesBase : public LayerProperties
   virtual nsIntRect ComputeDifferences(Layer* aRoot, 
                                        NotifySubDocInvalidationFunc aCallback);
 
+  virtual void MoveBy(const nsIntPoint& aOffset);
+
   nsIntRect ComputeChange(NotifySubDocInvalidationFunc aCallback)
   {
     bool transformChanged = mTransform != mLayer->GetTransform();
@@ -343,6 +345,12 @@ LayerPropertiesBase::ComputeDifferences(Layer* aRoot, NotifySubDocInvalidationFu
     return ComputeChange(aCallback);
   }
 }
+  
+void 
+LayerPropertiesBase::MoveBy(const nsIntPoint& aOffset)
+{
+  mTransform.TranslatePost(gfxPoint3D(aOffset.x, aOffset.y, 0)); 
+}
 
 } // namespace layers
 } // namespace mozilla

gfx/layers/LayerTreeInvalidation.h

@@ -59,6 +59,9 @@ struct LayerProperties
    */
   virtual nsIntRect ComputeDifferences(Layer* aRoot, 
                                        NotifySubDocInvalidationFunc aCallback) = 0;
+  
+  
+  virtual void MoveBy(const nsIntPoint& aOffset) = 0;
 };
 
 } // namespace layers

layout/base/FrameLayerBuilder.cpp

@@ -2378,6 +2378,8 @@ FrameLayerBuilder::AddThebesDisplayItem(ThebesLayer* aLayer,
       tempManager->SetRoot(layer);
       layerBuilder->WillEndTransaction();
 
+      nsIntPoint offset = GetLastPaintOffset(aLayer) - GetTranslationForThebesLayer(aLayer);
+      props->MoveBy(-offset);
       nsIntRect invalid = props->ComputeDifferences(layer, nullptr);
       if (aLayerState == LAYER_SVG_EFFECTS) {
         invalid = nsSVGIntegrationUtils::AdjustInvalidAreaForSVGEffects(aItem->GetUnderlyingFrame(), invalid);