Bug 862180. Part 1: Remove null checks on the result of nsDisplayItem::GetUnderlyingFrame(). r=mattwoodrow

layout/base/FrameLayerBuilder.cpp

@@ -1128,7 +1128,6 @@ FrameLayerBuilder::GetOldLayerFor(nsDisplayItem* aItem,
   uint32_t key = aItem->GetPerFrameKey();
   nsIFrame* frame = aItem->GetUnderlyingFrame();
 
-  if (frame) {
   DisplayItemData* oldData = GetOldLayerForFrame(frame, key);
   if (oldData) {
     if (aOldGeometry) {
@@ -1145,7 +1144,6 @@ FrameLayerBuilder::GetOldLayerFor(nsDisplayItem* aItem,
     }
     return oldData->mLayer;
   }
-  }
 
   return nullptr;
 } 
@@ -2233,8 +2231,6 @@ ContainerState::InvalidateForLayerChange(nsDisplayItem* aItem,
                                          const nsPoint& aTopLeft,
                                          nsDisplayItemGeometry *aGeometry)
 {
-  NS_ASSERTION(aItem->GetUnderlyingFrame(),
-               "Display items that render using Thebes must have a frame");
   NS_ASSERTION(aItem->GetPerFrameKey(),
                "Display items that render using Thebes must have a key");
   nsDisplayItemGeometry *oldGeometry = NULL;
@@ -2383,7 +2379,6 @@ FrameLayerBuilder::AddThebesDisplayItem(ThebesLayer* aLayer,
     if (entry->mContainerLayerGeneration == 0) {
       entry->mContainerLayerGeneration = mContainerLayerGeneration;
     }
-    NS_ASSERTION(aItem->GetUnderlyingFrame(), "Must have frame");
     if (tempManager) {
       FrameLayerBuilder* layerBuilder = new FrameLayerBuilder();
       layerBuilder->Init(mDisplayListBuilder, tempManager);
@@ -2960,8 +2955,6 @@ Layer*
 FrameLayerBuilder::GetLeafLayerFor(nsDisplayListBuilder* aBuilder,
                                    nsDisplayItem* aItem)
 {
-  NS_ASSERTION(aItem->GetUnderlyingFrame(),
-               "Can only call GetLeafLayerFor on items that have a frame");
   Layer* layer = GetOldLayerFor(aItem);
   if (!layer)
     return nullptr;
@@ -3293,9 +3286,7 @@ FrameLayerBuilder::DrawThebesLayer(ThebesLayer* aLayer,
       PaintInactiveLayer(builder, cdi->mInactiveLayerManager, cdi->mItem, aContext, rc);
     } else {
       nsIFrame* frame = cdi->mItem->GetUnderlyingFrame();
-      if (frame) {
       frame->AddStateBits(NS_FRAME_PAINTED_THEBES);
-      }
 #ifdef MOZ_DUMP_PAINTING
 
       if (gfxUtils::sDumpPainting) {

layout/base/nsDisplayList.cpp

@@ -939,7 +939,7 @@ TreatAsOpaque(nsDisplayItem* aItem, nsDisplayListBuilder* aBuilder)
     // be treated as opaque (and their bounds is just the union of their
     // children, which might be a large area their contents don't really cover).
     nsIFrame* f = aItem->GetUnderlyingFrame();
-    if (f && f->PresContext()->IsChrome() && !aItem->GetChildren() &&
+    if (f->PresContext()->IsChrome() && !aItem->GetChildren() &&
         f->StyleDisplay()->mOpacity != 0.0) {
       opaque = aItem->GetBounds(aBuilder, &snap);
     }
@@ -1440,8 +1440,7 @@ static bool IsContentLEQ(nsDisplayItem* aItem1, nsDisplayItem* aItem2,
 
 static bool IsZOrderLEQ(nsDisplayItem* aItem1, nsDisplayItem* aItem2,
                         void* aClosure) {
-  // These GetUnderlyingFrame calls return non-null because we're only used
-  // in sorting.  Note that we can't just take the difference of the two
+  // Note that we can't just take the difference of the two
   // z-indices here, because that might overflow a 32-bit int.
   int32_t index1 = nsLayoutUtils::GetZIndex(aItem1->GetUnderlyingFrame());
   int32_t index2 = nsLayoutUtils::GetZIndex(aItem2->GetUnderlyingFrame());
@@ -2649,10 +2648,9 @@ nsDisplayWrapList::RequiredLayerStateForChildren(nsDisplayListBuilder* aBuilder,
   LayerState result = LAYER_INACTIVE;
   for (nsDisplayItem* i = aList.GetBottom(); i; i = i->GetAbove()) {
     nsIFrame* f = i->GetUnderlyingFrame();
-    if (f) {
     nsIFrame* activeScrolledRoot =
       nsLayoutUtils::GetActiveScrolledRootFor(f, nullptr);
-      if (activeScrolledRoot != aActiveScrolledRoot && result == LAYER_INACTIVE)
+    if (activeScrolledRoot != aActiveScrolledRoot && result == LAYER_INACTIVE) {
       result = LAYER_ACTIVE;
     }
 

layout/base/nsLayoutUtils.cpp

@@ -1081,9 +1081,6 @@ nsLayoutUtils::GetActiveScrolledRootFor(nsDisplayItem* aItem,
   if (aShouldFixToViewport) {
     *aShouldFixToViewport = false;
   }
-  if (!f) {
-    return nullptr;
-  }
   if (aItem->ShouldFixToViewport(aBuilder)) {
     if (aShouldFixToViewport) {
       *aShouldFixToViewport = true;

layout/base/nsPresShell.cpp

@@ -4493,7 +4493,6 @@ PresShell::ClipListToRange(nsDisplayListBuilder *aBuilder,
     // temporary list. If null, no item should be inserted.
     nsDisplayItem* itemToInsert = nullptr;
     nsIFrame* frame = i->GetUnderlyingFrame();
-    if (frame) {
     nsIContent* content = frame->GetContent();
     if (content) {
       bool atStart = (content == aRange->GetStartParent());
@@ -4545,7 +4544,6 @@ PresShell::ClipListToRange(nsDisplayListBuilder *aBuilder,
         }
       }
     }
-    }
 
     // insert the item into the list if necessary. If the item has a child
     // list, insert that as well
@@ -5282,7 +5280,6 @@ PresShell::MarkImagesInListVisible(const nsDisplayList& aList)
     nsIFrame* f = item->GetUnderlyingFrame();
     // We could check the type of the display item, only a handful can hold an
     // image loading content.
-    if (f) {
     // dont bother nscomptr here, it is wasteful
     nsCOMPtr<nsIImageLoadingContent> content(do_QueryInterface(f->GetContent()));
     if (content) {
@@ -5295,7 +5292,6 @@ PresShell::MarkImagesInListVisible(const nsDisplayList& aList)
     }
   }
 }
-}
 
 void
 PresShell::RebuildImageVisibility(const nsDisplayList& aList)

layout/generic/TextOverflow.cpp

@@ -627,7 +627,7 @@ TextOverflow::PruneDisplayListContents(nsDisplayList*        aList,
   nsDisplayItem* item;
   while ((item = aList->RemoveBottom())) {
     nsIFrame* itemFrame = item->GetUnderlyingFrame();
-    if (itemFrame && IsFrameDescendantOfAny(itemFrame, aFramesToHide, mBlock)) {
+    if (IsFrameDescendantOfAny(itemFrame, aFramesToHide, mBlock)) {
       item->~nsDisplayItem();
       continue;
     }

layout/generic/nsFrame.cpp

@@ -1673,8 +1673,7 @@ WrapPreserve3DListInternal(nsIFrame* aFrame, nsDisplayListBuilder *aBuilder, nsD
     // and then flush this list into aOutput by wrapping the whole lot with a single
     // nsDisplayTransform.
 
-    if (childFrame &&
-        childFrame->GetParent() &&
+    if (childFrame->GetParent() &&
         (childFrame->GetParent()->Preserves3DChildren() || childFrame == aFrame)) {
       switch (item->GetType()) {
         case nsDisplayItem::TYPE_TRANSFORM: {
@@ -1869,7 +1868,6 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
     nsDisplayItem* item = set.PositionedDescendants()->GetBottom();
     if (item) {
       nsIFrame* f = item->GetUnderlyingFrame();
-      NS_ASSERTION(f, "After sorting, every item in the list should have an underlying frame");
       if (nsLayoutUtils::GetZIndex(f) < 0) {
         set.PositionedDescendants()->RemoveBottom();
         resultList.AppendToTop(item);

layout/generic/nsPageFrame.cpp

@@ -421,7 +421,7 @@ PruneDisplayListForExtraPage(nsDisplayListBuilder* aBuilder,
       i->UpdateBounds(aBuilder);
     } else {
       nsIFrame* f = i->GetUnderlyingFrame();
-      if (!f || !nsLayoutUtils::IsProperAncestorFrameCrossDoc(aPage, f)) {
+      if (!nsLayoutUtils::IsProperAncestorFrameCrossDoc(aPage, f)) {
         // We're throwing this away so call its destructor now. The memory
         // is owned by aBuilder which destroys all items at once.
         i->~nsDisplayItem();