Enable srcset support in HTMLImageElement

Source/wtf/text/StringView.h

Index: Source/wtf/text/StringView.h
diff --git a/Source/wtf/text/StringView.h b/Source/wtf/text/StringView.h
index 40d1866cf1dc4c277cd3fe51ebafe7358251efae..dc92fa346564c06b3dc7901ad4ab7fa211222e83 100644
--- a/Source/wtf/text/StringView.h
+++ b/Source/wtf/text/StringView.h
@@ -86,6 +86,15 @@ public:
         return m_impl->characters16() + m_offset;
     }
 
+    PassRefPtr<StringImpl> toString() const
+    {
+        if (!m_impl)
+            return m_impl;
+        if (m_impl->is8Bit())
+            return StringImpl::create(characters8(), m_length);
+        return StringImpl::create(characters16(), m_length);

[abarth-chromium, 2013/09/20 21:13:34]

We should probably add an optimization when m_offset is zero and m_length ==
m_impl->length().  In that case, we can just return m_impl instead of making a
copy.

+    }
+
 private:
     RefPtr<StringImpl> m_impl;
     unsigned m_offset;