Bug 1041512 - Mark intrinsic widths dirty on a style change even if the frame hasn't had its first reflow yet. r=dbaron

layout/base/RestyleManager.cpp

@@ -501,11 +501,6 @@ RestyleManager::RecomputePosition(nsIFrame* aFrame)
 void
 RestyleManager::StyleChangeReflow(nsIFrame* aFrame, nsChangeHint aHint)
 {
-  // If the frame hasn't even received an initial reflow, then don't
-  // send it a style-change reflow!
-  if (aFrame->GetStateBits() & NS_FRAME_FIRST_REFLOW)
-    return;
-
   nsIPresShell::IntrinsicDirty dirtyType;
   if (aHint & nsChangeHint_ClearDescendantIntrinsics) {
     NS_ASSERTION(aHint & nsChangeHint_ClearAncestorIntrinsics,
@@ -518,18 +513,23 @@ RestyleManager::StyleChangeReflow(nsIFrame* aFrame, nsChangeHint aHint)
   }
 
   nsFrameState dirtyBits;
-  if (aHint & nsChangeHint_NeedDirtyReflow) {
+  if (aFrame->GetStateBits() & NS_FRAME_FIRST_REFLOW) {
+    dirtyBits = nsFrameState(0);
+  } else if (aHint & nsChangeHint_NeedDirtyReflow) {
     dirtyBits = NS_FRAME_IS_DIRTY;
   } else {
     dirtyBits = NS_FRAME_HAS_DIRTY_CHILDREN;
   }
 
+  // If we're not going to clear any intrinsic sizes on the frames, and
+  // there are no dirty bits to set, then there's nothing to do.
+  if (dirtyType == nsIPresShell::eResize && !dirtyBits)
+    return;
+
   do {
     mPresContext->PresShell()->FrameNeedsReflow(aFrame, dirtyType, dirtyBits);
     aFrame = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(aFrame);
   } while (aFrame);
-
-  return;
 }
 
 void

layout/base/nsIPresShell.h

@@ -495,9 +495,13 @@ public:
   /**
    * Tell the pres shell that a frame needs to be marked dirty and needs
    * Reflow.  It's OK if this is an ancestor of the frame needing reflow as
-   * long as the ancestor chain between them doesn't cross a reflow root.  The
-   * bit to add should be either NS_FRAME_IS_DIRTY or
-   * NS_FRAME_HAS_DIRTY_CHILDREN (but not both!).
+   * long as the ancestor chain between them doesn't cross a reflow root.
+   *
+   * The bit to add should be NS_FRAME_IS_DIRTY, NS_FRAME_HAS_DIRTY_CHILDREN
+   * or nsFrameState(0); passing 0 means that dirty bits won't be set on the
+   * frame or its ancestors/descendants, but that intrinsic widths will still
+   * be marked dirty.  Passing aIntrinsicDirty = eResize and aBitToAdd = 0
+   * would result in no work being done, so don't do that.
    */
   enum IntrinsicDirty {
     // XXXldb eResize should be renamed

layout/base/nsPresShell.cpp

@@ -2775,10 +2775,11 @@ PresShell::FrameNeedsReflow(nsIFrame *aFrame, IntrinsicDirty aIntrinsicDirty,
                             nsFrameState aBitToAdd)
 {
   NS_PRECONDITION(aBitToAdd == NS_FRAME_IS_DIRTY ||
-                  aBitToAdd == NS_FRAME_HAS_DIRTY_CHILDREN,
+                  aBitToAdd == NS_FRAME_HAS_DIRTY_CHILDREN ||
+                  !aBitToAdd,
                   "Unexpected bits being added");
-  NS_PRECONDITION(aIntrinsicDirty != eStyleChange ||
-                  aBitToAdd == NS_FRAME_IS_DIRTY,
+  NS_PRECONDITION(!(aIntrinsicDirty == eStyleChange &&
+                    aBitToAdd == NS_FRAME_HAS_DIRTY_CHILDREN),
                   "bits don't correspond to style change reason");
 
   NS_ASSERTION(!mIsReflowing, "can't mark frame dirty during reflow");
@@ -2876,6 +2877,11 @@ PresShell::FrameNeedsReflow(nsIFrame *aFrame, IntrinsicDirty aIntrinsicDirty,
       } while (stack.Length() != 0);
     }
 
+    // Skip setting dirty bits up the tree if we weren't given a bit to add.
+    if (!aBitToAdd) {
+      continue;
+    }
+
     // Set NS_FRAME_HAS_DIRTY_CHILDREN bits (via nsIFrame::ChildIsDirty)
     // up the tree until we reach either a frame that's already dirty or
     // a reflow root.