Check for Unicode in Font before ICU call

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 e44d55753560c693ca44de87c11439bebc244319..0f602c32b96b633015922f9a5669f16a0a4c4109 100644
--- a/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
+++ b/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
@@ -359,17 +359,37 @@ static void normalizeCharacters(const TextRun& run, unsigned length, UChar* dest
         source = run.characters16();
     }
 
+    // Convert to NFC form if the text has diacritical marks. In most of the font, OTF rules
+    // for diacritical marks are missing. Using ICU calls to convert to final form and then pass
+    // updated Unicode string to Harfbuzz.
+    icu::UnicodeString normalizedString;
+    UErrorCode errorICU = U_ZERO_ERROR;
+    bool isDiacriticalMarkPresent = false;
+
     *destinationLength = 0;
     while (position < length) {
         UChar32 character;
         U16_NEXT(source, position, length, character);
         // Don't normalize tabs as they are not treated as spaces for word-end.
-        if (run.normalizeSpace() && Character::isNormalizedCanvasSpaceCharacter(character))
+        if (run.normalizeSpace() && Character::isNormalizedCanvasSpaceCharacter(character)) {
             character = spaceCharacter;
-        else if (Character::treatAsSpace(character) && character != tabulationCharacter)
+        } else if (Character::treatAsSpace(character) && character != tabulationCharacter) {
             character = spaceCharacter;
-        else if (Character::treatAsZeroWidthSpaceInComplexScript(character))
+        } else if (Character::treatAsZeroWidthSpaceInComplexScript(character)) {
             character = zeroWidthSpaceCharacter;
+        } else if (!isDiacriticalMarkPresent && ::ublock_getCode(character) == UBLOCK_COMBINING_DIACRITICAL_MARKS) {
+            isDiacriticalMarkPresent = true;
+            icu::Normalizer::normalize(icu::UnicodeString(source, length), UNORM_NFC, 0 , normalizedString, errorICU);
+            if (U_FAILURE(errorICU)) {
+                normalizedString.remove();
+            } else if (!normalizedString.isEmpty()) {
+                *destinationLength = 0;
+                position = 0;
+                length = static_cast<int>(normalizedString.length());
+                source = normalizedString.getBuffer();
+                continue;
+            }
+        }
 
         U16_APPEND(destination, *destinationLength, length, character, error);
         ASSERT_UNUSED(error, !error);