Merge 108111 - REGRESSION: empty span creates renders with non-zero height

Source/WebCore/rendering/RenderBlockLineLayout.cpp

Index: Source/WebCore/rendering/RenderBlockLineLayout.cpp
===================================================================
--- Source/WebCore/rendering/RenderBlockLineLayout.cpp	(revision 109045)
+++ Source/WebCore/rendering/RenderBlockLineLayout.cpp	(working copy)
@@ -491,6 +491,9 @@
         if (runCount == 2 && !r->m_object->isListMarker())
             isOnlyRun = (!style()->isLeftToRightDirection() ? bidiRuns.lastRun() : bidiRuns.firstRun())->m_object->isListMarker();
 
+        if (lineInfo.isEmpty())
+            continue;
+
         InlineBox* box = createInlineBoxForRenderer(r->m_object, false, isOnlyRun);
         r->m_box = box;
 
@@ -1824,14 +1827,22 @@
         || (whitespacePosition == TrailingWhitespace && style->whiteSpace() == PRE_WRAP && (!lineInfo.isEmpty() || !lineInfo.previousLineBrokeCleanly()));
 }
 
-static bool inlineFlowRequiresLineBox(RenderInline* flow, const LineInfo& lineInfo)
+static bool requiresLineBoxForContent(RenderInline* flow, const LineInfo& lineInfo)
 {
+    RenderObject* parent = flow->parent();
+    if (flow->document()->inNoQuirksMode() 
+        && (flow->style(lineInfo.isFirstLine())->lineHeight() != parent->style(lineInfo.isFirstLine())->lineHeight()
+        || flow->style()->verticalAlign() != parent->style()->verticalAlign()
+        || !parent->style()->font().fontMetrics().hasIdenticalAscentDescentAndLineGap(flow->style()->font().fontMetrics())))
+        return true;
+    return false;
+}
+
+static bool alwaysRequiresLineBox(RenderInline* flow, const LineInfo& lineInfo)
+{
     // FIXME: Right now, we only allow line boxes for inlines that are truly empty.
     // We need to fix this, though, because at the very least, inlines containing only
     // ignorable whitespace should should also have line boxes.
-    if (!flow->document()->inQuirksMode() && flow->style(lineInfo.isFirstLine())->lineHeight() != flow->parent()->style(lineInfo.isFirstLine())->lineHeight())
-        return true;
-
     return !flow->firstChild() && flow->hasInlineDirectionBordersPaddingOrMargin();
 }
 
@@ -1840,7 +1851,7 @@
     if (it.m_obj->isFloatingOrPositioned())
         return false;
 
-    if (it.m_obj->isRenderInline() && !inlineFlowRequiresLineBox(toRenderInline(it.m_obj), lineInfo))
+    if (it.m_obj->isRenderInline() && !alwaysRequiresLineBox(toRenderInline(it.m_obj), lineInfo) && !requiresLineBoxForContent(toRenderInline(it.m_obj), lineInfo))
         return false;
 
     if (!shouldCollapseWhiteSpace(it.m_obj->style(), lineInfo, whitespacePosition) || it.m_obj->isBR())
@@ -2228,8 +2239,12 @@
             // to make sure that we stop to include this object and then start ignoring spaces again.
             // If this object is at the start of the line, we need to behave like list markers and
             // start ignoring spaces.
-            if (inlineFlowRequiresLineBox(flowBox, lineInfo)) {
-                lineInfo.setEmpty(false, m_block, &width);
+            bool requiresLineBox = alwaysRequiresLineBox(flowBox, lineInfo);
+            if (requiresLineBox || requiresLineBoxForContent(flowBox, lineInfo)) {
+                // An empty inline that only has line-height, vertical-align or font-metrics will only get a
+                // line box to affect the height of the line if the rest of the line is not empty.
+                if (requiresLineBox)
+                    lineInfo.setEmpty(false, m_block, &width);
                 if (ignoringSpaces) {
                     trailingObjects.clear();
                     addMidpoint(lineMidpointState, InlineIterator(0, current.m_obj, 0)); // Stop ignoring spaces.