Strip anonymous wrappers when a block flow no longer requires them

Source/core/layout/LayoutBlock.cpp

Index: Source/core/layout/LayoutBlock.cpp
diff --git a/Source/core/layout/LayoutBlock.cpp b/Source/core/layout/LayoutBlock.cpp
index 116c979367c9b7c7fc0eb820d6eeff761531ee70..bd2ae4a4dacab025edc67144fad8e415dd676973 100644
--- a/Source/core/layout/LayoutBlock.cpp
+++ b/Source/core/layout/LayoutBlock.cpp
@@ -449,6 +449,21 @@ void LayoutBlock::addChildIgnoringContinuation(LayoutObject* newChild, LayoutObj
             LayoutBlock* newBox = createAnonymousBlock();
             LayoutBox::addChild(newBox, beforeChild);
             newBox->addChild(newChild);
+            LayoutObject* nextChild = beforeChild;
+            // Reparent adjacent inline siblings to the new box.

[mstensho (USE GERRIT), 2015/08/26 19:44:15]

As szager has already pointed out, how could there be inline siblings here?
We're in a block with block children.

Why don't we look at preceding siblings as well?

Making sure that we don't have extraneous anonymous block seems important, but
why don't we just try a bit harder to locate an anonymous block earlier instead
of creating a new one and deleting the old one? I'm talking about the "if
(afterChild && afterChild->isAnonymousBlock())" thing a bit further up. If your
new code finds an anonymous block, it means that we could have just used it in
the first place, instead of creating a new one and deleting the old one.

So, I'm thinking that I'd like to see:

1. Look harder for an existing anonymous block
2. If none can be found, create a new one, put the inline there, and reparent
adjacent (after AND before) floats and out-of-flow objects

One more thing: your changes here may lead to the situation where we have a
block-children-block whose only child is an anonymous block to contain inlines.
I dare you get rid of that redundant anonymous block and turn this parent block
into an inline-children-block! :) LayoutBlock::removeChild() already does it
when it happens ("The removal has knocked us down to containing only a single
anonymous box").

+            while (nextChild && (nextChild->isFloatingOrOutOfFlowPositioned() || nextChild->isInline() || nextChild->isAnonymousBlock())) {

[szager1, 2015/08/26 17:04:40]

nextChild->isInline() should never be true here

+                LayoutObject* sibling = nextChild->nextSibling();
+                if (nextChild->isAnonymousBlock()) {
+                    LayoutBlockFlow* nextBlock = toLayoutBlockFlow(nextChild);
+                    nextBlock->moveAllChildrenIncludingFloatsTo(newBox, true);
+                    // Delete the now-empty block's lines and nuke it.
+                    nextBlock->deleteLineBoxTree();

[szager1, 2015/08/26 17:04:40]

Redundant?  nextBlock->moveAllChildrenIncludingFloatsTo() should delete the line
box tree.

+                    nextBlock->destroy();
+                } else {
+                    moveChildTo(newBox, nextChild, 0, true);
+                }
+                nextChild = sibling;
+            }
             return;
         }
     }