Include <algorithm> if you use functions from <algorithm>.

third_party/WebKit/Source/core/html/parser/HTMLSrcsetParser.cpp

 /*
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 23 matching lines @@
 
 #include "core/dom/Document.h"
 #include "core/fetch/MemoryCache.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/frame/FrameConsole.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/UseCounter.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "platform/ParsingUtilities.h"
+#include <algorithm>
 
 namespace blink {
 
 static bool compareByDensity(const ImageCandidate& first, const ImageCandidate& second)
 {
     return first.density() < second.density();
 }
 
 enum DescriptorTokenizerState {
     TokenStart,
@@ skipping 381 matching lines @@
     Vector<ImageCandidate> imageCandidates;
     imageCandidates.append(srcsetImageCandidate);
 
     if (!srcAttribute.isEmpty())
         imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), DescriptorParsingResult(), ImageCandidate::SrcOrigin));
 
     return pickBestImageCandidate(deviceScaleFactor, sourceSize, imageCandidates).toString();
 }
 
 }