Expand WTF::StringView's API to be more like StringPiece.

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

 /*
  * 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 68 matching lines @@
     };
 
     ImageCandidate()
         : m_density(1.0)
         , m_resourceWidth(UninitializedDescriptor)
         , m_originAttribute(SrcsetOrigin)
     {
     }
 
     ImageCandidate(const String& source, unsigned start, unsigned length, const DescriptorParsingResult& result, OriginAttribute originAttribute)
-        : m_string(source.createView(start, length))
-        , m_density(result.hasDensity()?result.density():UninitializedDescriptor)
-        , m_resourceWidth(result.hasWidth()?result.getResourceWidth():UninitializedDescriptor)
+        : m_source(source)
+        , m_string(source, start, length)
+        , m_density(result.hasDensity() ? result.density() : UninitializedDescriptor)
+        , m_resourceWidth(result.hasWidth() ? result.getResourceWidth() : UninitializedDescriptor)
         , m_originAttribute(originAttribute)
     {
     }
 
     String toString() const
     {
-        return String(m_string.toString());
+        return m_string.toString();
     }
 
     AtomicString url() const
     {
-        return AtomicString(m_string.toString());
+        return AtomicString(toString());
     }
 
     void setDensity(float factor)
     {
         m_density = factor;
     }
 
     float density() const
     {
         return m_density;
     }
 
     int getResourceWidth() const
     {
         return m_resourceWidth;
     }
 
     bool srcOrigin() const
     {
         return (m_originAttribute == SrcOrigin);
     }
 
     inline bool isEmpty() const
     {
         return m_string.isEmpty();
     }
 
 private:
+    String m_source; // Keep the StringView buffer alive.
     StringView m_string;
     float m_density;
     int m_resourceWidth;
     OriginAttribute m_originAttribute;
 };
 
 ImageCandidate bestFitSourceForSrcsetAttribute(float deviceScaleFactor, float sourceSize, const String& srcsetAttribute, Document* = nullptr);
 
 CORE_EXPORT ImageCandidate bestFitSourceForImageAttributes(float deviceScaleFactor, float sourceSize, const String& srcAttribute, const String& srcsetAttribute, Document* = nullptr);
 
 String bestFitSourceForImageAttributes(float deviceScaleFactor, float sourceSize, const String& srcAttribute, ImageCandidate& srcsetImageCandidate);
 
 } // namespace blink
 
 #endif