Empty inline elements always get a line box.

Source/core/rendering/line/BreakingContextInlineHeaders.h

Index: Source/core/rendering/line/BreakingContextInlineHeaders.h
diff --git a/Source/core/rendering/line/BreakingContextInlineHeaders.h b/Source/core/rendering/line/BreakingContextInlineHeaders.h
index 5a148ca4b6a418b208cb766c1f123ac426f0a6dc..f99965e1400b4ed24d6b5b35db7f638ad1b32b4a 100644
--- a/Source/core/rendering/line/BreakingContextInlineHeaders.h
+++ b/Source/core/rendering/line/BreakingContextInlineHeaders.h
@@ -419,23 +419,24 @@ inline void BreakingContext::handleEmptyInline()
 
     RenderInline* flowBox = toRenderInline(m_current.object());
 
-    // Now that some inline flows have line boxes, if we are already ignoring spaces, we need
-    // 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.
     bool requiresLineBox = alwaysRequiresLineBox(m_current.object());
     if (requiresLineBox || requiresLineBoxForContent(flowBox, m_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.
+        // An empty inline that only has line-height, vertical-align or font-metrics will
+        // not force linebox creation (and thus affect the height of the line) if the rest of the line is empty.
         if (requiresLineBox)
             m_lineInfo.setEmpty(false, m_block, &m_width);
         if (m_ignoringSpaces) {
+            // If we are in a run of ignored spaces then ensure we get a linebox if lineboxes are eventually
+            // created for the line...
             m_trailingObjects.clear();
             m_lineMidpointState.ensureLineBoxInsideIgnoredSpaces(m_current.object());
+        } else if (m_currentCharacterIsSpace) {
+            // .. likewise if we come after a single space.
+            m_lineMidpointState.ensureLineBoxForRenderer(m_current.object());
         } else if (m_blockStyle->collapseWhiteSpace() && m_resolver.position().object() == m_current.object()
             && shouldSkipWhitespaceAfterStartObject(m_block, m_current.object(), m_lineMidpointState)) {
-            // Like with list markers, we start ignoring spaces to make sure that any
-            // additional spaces we see will be discarded.
+            // If this object is at the start of the line, we need to behave like list markers and
+            // start ignoring spaces.
             m_currentCharacterShouldCollapseIfPreWap = m_currentCharacterIsSpace = true;
             m_ignoringSpaces = true;
         }