Add StringBuilder::erase(index)

third_party/WebKit/Source/platform/wtf/text/StringBuilder.cpp

Index: third_party/WebKit/Source/platform/wtf/text/StringBuilder.cpp
diff --git a/third_party/WebKit/Source/platform/wtf/text/StringBuilder.cpp b/third_party/WebKit/Source/platform/wtf/text/StringBuilder.cpp
index 0e112bea782c58d0821612e139e5dd6ceae1320b..61c10dec5b8b845c3558f0c1b3cb7a5505bc3f40 100644
--- a/third_party/WebKit/Source/platform/wtf/text/StringBuilder.cpp
+++ b/third_party/WebKit/Source/platform/wtf/text/StringBuilder.cpp
@@ -230,4 +230,18 @@ void StringBuilder::AppendNumber(double number, unsigned precision) {
   Append(NumberToFixedPrecisionString(number, precision, buffer));
 }
 
+void StringBuilder::erase(unsigned index) {
+  if (index >= length_)
+    return;
+
+  if (is8_bit_) {
+    EnsureBuffer8(0);
+    buffer8_->erase(index);
+  } else {
+    EnsureBuffer16(0);
+    buffer16_->erase(index);
+  }
+  --length_;
+}
+
 }  // namespace WTF