Bindings: Add ScalarValueString support

Source/wtf/text/StringImpl.cpp

Index: Source/wtf/text/StringImpl.cpp
diff --git a/Source/wtf/text/StringImpl.cpp b/Source/wtf/text/StringImpl.cpp
index 838b6715fcdce7c992b8a90e4fcfaab69c36ac77..8ecf0face368396acbd9e95aff9ebab5bddf7e43 100644
--- a/Source/wtf/text/StringImpl.cpp
+++ b/Source/wtf/text/StringImpl.cpp
@@ -1893,6 +1893,74 @@ PassRefPtr<StringImpl> StringImpl::replace(StringImpl* pattern, StringImpl* repl
     return newImpl.release();
 }
 
+PassRefPtr<StringImpl> StringImpl::replaceUnpairedSurrogates()
+{
+    if (is8Bit())
+        return this;
+
+    const UChar* characters = characters16();
+    const unsigned length = m_length;
+
+    // Scan to see if there are any unmatched surrogates.
+    bool unmatched = false;
+    for (unsigned i = 0; i < length; ++i) {
+        UChar c = characters[i];
+        if (c < 0xD800 || c > 0xDFFF) {
+            // Non-surrogate - no-op.
+        } else if (0xDC00 <= c && c <= 0xDFFF) {
+            // Unmatched trail surrogate.
+            unmatched = true;
+            break;
+        } else if (i == length - 1) {
+            // Unmatched lead surrogate at EOF.
+            unmatched = true;
+            break;
+        } else {
+            UChar d = characters[i + 1];
+            if (0xDC00 <= d && d <= 0xDFFF) {
+                // Matching trail surrogate.
+                ++i;
+                continue;
+            }
+            // Unmatched lead.
+            unmatched = true;
+            break;
+        }
+    }
+    if (!unmatched)
+        return this;
+
+    UChar* data;
+    RefPtr<StringImpl> newImpl = createUninitialized(length, data);
+    for (unsigned i = 0; i < length; ++i) {
+        UChar c = characters[i];
+        if (c < 0xD800 || c > 0xDFFF) {
+            // Non-surrogate.
+            data[i] = c;
+        } else if (0xDC00 <= c && c <= 0xDFFF) {
+            // Unmatched trail surrogate.
+            data[i] = Unicode::replacementCharacter;
+        } else if (i == length - 1) {
+            // Unmatched lead surrogate at EOF.
+            data[i] = Unicode::replacementCharacter;
+        } else {
+            UChar d = characters[i + 1];
+            if (0xDC00 <= d && d <= 0xDFFF) {
+                // Matching trail surrogate.
+                data[i] = c;
+                data[i + 1] = d;
+                ++i;
+            } else {
+                // Unmatched lead.
+                data[i] = Unicode::replacementCharacter;
+            }
+        }
+    }
+
+    return newImpl.release();
+}
+
+
 PassRefPtr<StringImpl> StringImpl::upconvertedString()
 {
     if (is8Bit())