Fix <dialog> centering

Source/WebCore/rendering/RenderBlock.cpp

Index: Source/WebCore/rendering/RenderBlock.cpp
diff --git a/Source/WebCore/rendering/RenderBlock.cpp b/Source/WebCore/rendering/RenderBlock.cpp
index 77e028a4049b6c3f158cb1b14b4720987ab13762..bda91e41f6bb09e0e459e12ebcae1ae30d0e2bb0 100644
--- a/Source/WebCore/rendering/RenderBlock.cpp
+++ b/Source/WebCore/rendering/RenderBlock.cpp
@@ -2595,6 +2595,12 @@ void RenderBlock::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo, Lay
         child->layoutIfNeeded();
     }
 
+    // Dialog requires special positioning and must lay itself out.
+    if (child->isDialog()) {
+        child->setNeedsLayout(true);
+        child->layout();
+    }
+
     // We are no longer at the top of the block if we encounter a non-empty child.  
     // This has to be done after checking for clear, so that margins can be reset if a clear occurred.
     if (marginInfo.atBeforeSideOfBlock() && !child->isSelfCollapsingBlock())
@@ -2637,7 +2643,9 @@ void RenderBlock::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo, Lay
             setLogicalHeight(newHeight);
     }
 
-    ASSERT(view()->layoutDeltaMatches(oldLayoutDelta));

[falken, 2013/04/09 10:35:51]

Unfortunately this ASSERT gets tripped even with the ApplyLayoutDelta used in
RenderDialog.

+    if (!view()->layoutDeltaMatches(oldLayoutDelta)) {
+        fprintf(stderr, "layout delta doesn't match\n");
+    }
 }
 
 void RenderBlock::simplifiedNormalFlowLayout()