Bug 913443 - Extract layer hint calculation. r=roc

--HG--
extra : rebase_source : eee7b00b69b46e106865911e58a0b06a8643980e

layout/base/FrameLayerBuilder.cpp

@@ -698,6 +698,9 @@ public:
 protected:
   friend class PaintedLayerData;
 
+  LayerManager::PaintedLayerCreationHint
+    GetLayerCreationHint(const nsIFrame* aAnimatedGeometryRoot);
+
   /**
    * Grab the next recyclable PaintedLayer, or create one if there are no
    * more recyclable PaintedLayers. Does any necessary invalidation of
@@ -1681,6 +1684,22 @@ InvalidateEntirePaintedLayer(PaintedLayer* aLayer, const nsIFrame* aAnimatedGeom
   ResetScrollPositionForLayerPixelAlignment(aAnimatedGeometryRoot);
 }
 
+LayerManager::PaintedLayerCreationHint
+ContainerState::GetLayerCreationHint(const nsIFrame* aAnimatedGeometryRoot)
+{
+  // Check whether the layer will be scrollable. This is used as a hint to
+  // influence whether tiled layers are used or not.
+  if (mParameters.mInLowPrecisionDisplayPort) {
+    return LayerManager::SCROLLABLE;
+  }
+  nsIFrame* animatedGeometryRootParent = aAnimatedGeometryRoot->GetParent();
+  if (animatedGeometryRootParent &&
+      animatedGeometryRootParent->GetType() == nsGkAtoms::scrollFrame) {
+    return LayerManager::SCROLLABLE;
+  }
+  return LayerManager::NONE;
+}
+
 already_AddRefed<PaintedLayer>
 ContainerState::CreateOrRecyclePaintedLayer(const nsIFrame* aAnimatedGeometryRoot,
                                             const nsIFrame* aReferenceFrame,
@@ -1694,15 +1713,8 @@ ContainerState::CreateOrRecyclePaintedLayer(const nsIFrame* aAnimatedGeometryRoo
 
   // Check whether the layer will be scrollable. This is used as a hint to
   // influence whether tiled layers are used or not.
-  LayerManager::PaintedLayerCreationHint creationHint = LayerManager::NONE;
-  if (mParameters.mInLowPrecisionDisplayPort ) {
-    creationHint = LayerManager::SCROLLABLE;
-  }
-  nsIFrame* animatedGeometryRootParent = aAnimatedGeometryRoot->GetParent();
-  if (animatedGeometryRootParent &&
-      animatedGeometryRootParent->GetType() == nsGkAtoms::scrollFrame) {
-    creationHint = LayerManager::SCROLLABLE;
-  }
+  LayerManager::PaintedLayerCreationHint creationHint =
+    GetLayerCreationHint(aAnimatedGeometryRoot);
 
   if (mNextFreeRecycledPaintedLayer < mRecycledPaintedLayers.Length()) {
     // Try to recycle a layer