Relanding changes to replace local helpers with new nsLayoutUtils versions. r+sr=dbaron

layout/generic/nsBlockFrame.cpp

@@ -2421,20 +2421,11 @@ nsBlockFrame::AttributeChanged(PRInt32         aNameSpaceID,
   else if (nsGkAtoms::value == aAttribute) {
     const nsStyleDisplay* styleDisplay = GetStyleDisplay();
     if (NS_STYLE_DISPLAY_LIST_ITEM == styleDisplay->mDisplay) {
-      nsIFrame* nextAncestor = mParent;
-      nsBlockFrame* blockParent = nsnull;
-      
       // Search for the closest ancestor that's a block frame. We
       // make the assumption that all related list items share a
       // common block parent.
       // XXXldb I think that's a bad assumption.
-      while (nextAncestor) {
-        if (NS_OK == nextAncestor->QueryInterface(kBlockFrameCID, 
-                                                  (void**)&blockParent)) {
-          break;
-        }
-        nextAncestor = nextAncestor->GetParent();
-      }
+      nsBlockFrame* blockParent = nsLayoutUtils::FindNearestBlockAncestor(this);
 
       // Tell the enclosing block frame to renumber list items within
       // itself

layout/generic/nsHTMLReflowState.cpp

@@ -651,24 +651,6 @@ nsHTMLReflowState::CalculateHorizBorderPaddingMargin(nscoord aContainingBlockWid
          margin.left + margin.right;
 }
 
-static nsIFrame*
-FindImmediateChildOf(nsIFrame* aParent, nsIFrame* aDescendantFrame)
-{
-  nsIFrame* result = aDescendantFrame;
-
-  while (result) {
-    nsIFrame* parent = result->GetParent();
-    if (parent == aParent) {
-      break;
-    }
-
-    // The frame is not an immediate child of aParent so walk up another level
-    result = parent;
-  }
-
-  return result;
-}
-
 /**
  * Returns PR_TRUE iff a pre-order traversal of the normal child
  * frames rooted at aFrame finds no non-empty frame before aDescendant.
@@ -776,7 +758,8 @@ nsHTMLReflowState::CalculateHypotheticalBox(nsPresContext*    aPresContext,
                                   NS_REINTERPRET_CAST(void**, &blockFrame)))) {
     // We need the immediate child of the block frame, and that may not be
     // the placeholder frame
-    nsIFrame *blockChild = FindImmediateChildOf(blockFrame, aPlaceholderFrame);
+    nsIFrame *blockChild =
+      nsLayoutUtils::FindChildContainingDescendant(blockFrame, aPlaceholderFrame);
     nsBlockFrame::line_iterator lineBox = blockFrame->FindLineFor(blockChild);
 
     // How we determine the hypothetical box depends on whether the element