[inspector] Fix and refactor String16

src/inspector/v8-debugger-agent-impl.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/inspector/v8-debugger-agent-impl.h"
 
 #include <algorithm>
 
 #include "src/debug/debug-interface.h"
 #include "src/inspector/injected-script.h"
@@ skipping 58 matching lines @@
       return ":debug";
     case V8DebuggerAgentImpl::MonitorCommandBreakpointSource:
       return ":monitor";
   }
   return String16();
 }
 
 static String16 generateBreakpointId(
     const String16& scriptId, int lineNumber, int columnNumber,
     V8DebuggerAgentImpl::BreakpointSource source) {
-  return scriptId + ":" + String16::fromInteger(lineNumber) + ":" +
-         String16::fromInteger(columnNumber) + breakpointIdSuffix(source);
+  String16Builder builder;

[dgozman, 2016/11/15 15:32:25]

Just curious why builder and not concat with fromInteger()?

[Clemens Hammacher, 2016/11/15 17:00:44]

Performance ;)

+  builder.append(scriptId);
+  builder.append(':');
+  builder.appendNumber(lineNumber);
+  builder.append(':');
+  builder.appendNumber(columnNumber);
+  builder.append(breakpointIdSuffix(source));
+  return builder.toString();
 }
 
 static bool positionComparator(const std::pair<int, int>& a,
                                const std::pair<int, int>& b) {
   if (a.first != b.first) return a.first < b.first;
   return a.second < b.second;
 }
 
 static std::unique_ptr<protocol::Debugger::Location> buildProtocolLocation(
     const String16& scriptId, int lineNumber, int columnNumber) {
@@ skipping 1133 matching lines @@
 
 void V8DebuggerAgentImpl::reset() {
   if (!enabled()) return;
   m_scheduledDebuggerStep = NoStep;
   m_scripts.clear();
   m_blackboxedPositions.clear();
   m_breakpointIdToDebuggerBreakpointIds.clear();
 }
 
 }  // namespace v8_inspector