Use SizesAttributeParser to get the right srcset resource

Source/core/css/parser/SizesAttributeParserTest.cpp

 // Copyright 2014 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.
 
 #include "config.h"
 #include "core/css/parser/SizesAttributeParser.h"
 
 #include "core/css/MediaValuesCached.h"
 
 #include <gtest/gtest.h>
@@ skipping 28 matching lines @@
         {" /**/ ", 500},
         {" /**/ 300px", 300},
         {"300px /**/ ", 300},
         {" /**/ (min-width:500px) /**/ 300px", 300},
         {"-100px, 200px", 200},
         {"-50vw, 20vw", 100},
         {"50asdf, 200px", 200},
         {"asdf, 200px", 200},
         {"(max-width: 3000px) 200w, 400w", 500},
         {",, , /**/ ,200px", 200},
+        {"50vw", 250},
         // FIXME - test all other units, zero length and calc().
         {0, 0} // Do not remove the terminator line.
     };
 
     MediaValuesCached::MediaValuesCachedData data;
     data.viewportWidth = 500;
     data.viewportHeight = 500;
     data.deviceWidth = 500;
     data.deviceHeight = 500;
     data.devicePixelRatio = 2.0;
     data.colorBitsPerComponent = 24;
     data.monochromeBitsPerComponent = 0;
     data.pointer = MediaValues::MousePointer;
     data.defaultFontSize = 16;
     data.threeDEnabled = true;
     data.scanMediaType = false;
     data.screenMediaType = true;
     data.printMediaType = false;
     data.strictMode = true;
     RefPtr<MediaValues> mediaValues = MediaValuesCached::create(data);
 
     for (unsigned i = 0; testCases[i].input; ++i) {
         int effectiveSize = SizesAttributeParser::findEffectiveSize(testCases[i].input, mediaValues);
         ASSERT_EQ(testCases[i].output, effectiveSize);
     }
 }
 
 } // namespace