Use following font data and script for heading zero-width spaces while collecting candidate runs.

Source/platform/fonts/shaping/HarfBuzzShaper.cpp

Index: Source/platform/fonts/shaping/HarfBuzzShaper.cpp
diff --git a/Source/platform/fonts/shaping/HarfBuzzShaper.cpp b/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
index 535e173526421151cab4f1cda52923fdc6747fea..760edf85b04ea5c5c8be51ae77a02d0bc7544011 100644
--- a/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
+++ b/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
@@ -623,6 +623,10 @@ static inline bool collectCandidateRuns(const UChar* normalizedBuffer,
     if (!iterator.consume(character, clusterLength))
         return false;
 
+    bool collectionForHeadingZWS = false;
+    if (Character::treatAsZeroWidthSpace(character))
+        collectionForHeadingZWS = true;
+
     const SimpleFontData* nextFontData = font->glyphDataForCharacter(character, false, isSpaceNormalize).fontData;
     UErrorCode errorCode = U_ZERO_ERROR;
     UScriptCode nextScript = uscript_getScript(character, &errorCode);
@@ -651,8 +655,13 @@ static inline bool collectCandidateRuns(const UChar* normalizedBuffer,
                 return false;
             if (lastCharacter == zeroWidthJoiner)
                 currentFontData = nextFontData;
-            if ((nextFontData != currentFontData) || ((currentScript != nextScript) && (nextScript != USCRIPT_INHERITED) && (!uscript_hasScript(character, currentScript))))
-                break;
+            if ((nextFontData != currentFontData) || ((currentScript != nextScript) && (nextScript != USCRIPT_INHERITED) && (!uscript_hasScript(character, currentScript)))) {
+                if (!collectionForHeadingZWS)
+                    break;
+                currentFontData = nextFontData;
+                currentScript = nextScript;
+                collectionForHeadingZWS = false;
+            }
             currentCharacterPosition = iterator.characters();
             lastCharacter = character;
         }