Use StringBuilder::appendLiteral() / StringBuilder::append(char) when possible

Source/platform/text/PlatformLocale.cpp

Index: Source/platform/text/PlatformLocale.cpp
diff --git a/Source/platform/text/PlatformLocale.cpp b/Source/platform/text/PlatformLocale.cpp
index 73cb6e19c52594957b24fc3d8f78e7dc76add0ff..79991ced8991997c2314e1c712930aaa6b0e1169 100644
--- a/Source/platform/text/PlatformLocale.cpp
+++ b/Source/platform/text/PlatformLocale.cpp
@@ -82,7 +82,7 @@ String DateTimeStringBuilder::zeroPadString(const String& string, size_t width)
     StringBuilder zeroPaddedStringBuilder;
     zeroPaddedStringBuilder.reserveCapacity(width);
     for (size_t i = string.length(); i < width; ++i)
-        zeroPaddedStringBuilder.append("0");
+        zeroPaddedStringBuilder.append('0');
     zeroPaddedStringBuilder.append(string);
     return zeroPaddedStringBuilder.toString();
 }
@@ -364,7 +364,7 @@ String Locale::convertFromLocalizedNumber(const String& localized)
     StringBuilder builder;
     builder.reserveCapacity(input.length());
     if (isNegative)
-        builder.append("-");
+        builder.append('-');
     for (unsigned i = startIndex; i < endIndex;) {
         unsigned symbolIndex = matchedDecimalSymbolIndex(input, i);
         if (symbolIndex >= DecimalSymbolsSize)