Make blink::protocol::StringBuilder a distinct type from WTF::StringBuilder.

content/browser/devtools/protocol_string.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_DEVTOOLS_PROTOCOL_STRING_H
 #define CONTENT_BROWSER_DEVTOOLS_PROTOCOL_STRING_H
 
 #include <memory>
 #include <string>
 
@@ skipping 35 matching lines @@
   static String fromInteger(int number) {
     return base::IntToString(number);
   }
   static String fromDouble(double number) {
     String s = base::DoubleToString(number);
     if (!s.empty() && s[0] == '.')
       s = "0" + s;
     return s;
   }
   static const size_t kNotFound = static_cast<size_t>(-1);
+  static void builderAppend(StringBuilder& builder, const String& s) {
+    builder.append(s);
+  }
+  static void builderAppend(StringBuilder& builder, char c) {
+    builder.append(c);
+  }
+  static void builderAppend(StringBuilder& builder, const char* s, size_t len) {
+    builder.append(s, len);
+  }
   static void builderReserve(StringBuilder& builder, unsigned capacity) {
     builder.reserveCapacity(capacity);
   }
+  static String builderToString(StringBuilder& builder) {
+    return builder.toString();
+  }
   static std::unique_ptr<protocol::Value> parseJSON(const String&);
 };
 
 std::unique_ptr<protocol::Value> toProtocolValue(
     const base::Value* value, int depth);
 std::unique_ptr<base::Value> toBaseValue(protocol::Value* value, int depth);
 
 }  // namespace protocol
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DEVTOOLS_PROTOCOL_STRING_H