Remove base::StringValue

tools/win/DebugVisualizers/chrome.natvis

 <?xml version="1.0" encoding="utf-8" ?>
 <AutoVisualizer
     xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
   <Type Name="gfx::Point">
     <AlternativeType Name="gfx::PointF"/>
     <DisplayString>({x_}, {y_})</DisplayString>
     <Expand>
       <Item Name="X">x_</Item>
       <Item Name="Y">y_</Item>
     </Expand>
@@ skipping 219 matching lines @@
   </Type>
   <Type Name="base::Value">
     <DisplayString>Fundamental</DisplayString>
     <Expand>
       <ExpandedItem>(base::Value*)this,nd</ExpandedItem>
       <Item Name="Int">integer_value_</Item>
       <Item Name="Bool">boolean_value_</Item>
       <Item Name="Double">double_value_</Item>
     </Expand>
   </Type>
-  <Type Name="base::StringValue">
+  <Type Name="base::Value">
     <DisplayString>String ({value_})</DisplayString>
     <Expand>
       <ExpandedItem>(base::Value*)this,nd</ExpandedItem>
       <Item Name="Value">value_</Item>
     </Expand>
   </Type>
   <Type Name="base::BinaryValue">
     <DisplayString>Binary ({size_} byte(s))</DisplayString>
     <Expand>
       <ExpandedItem>(base::Value*)this,nd</ExpandedItem>
       <Item Name="Data">buffer_</Item>
     </Expand>
   </Type>
   <Type Name="base::DictionaryValue">
     <DisplayString>Dictionary ({dictionary_._Mysize} entries)</DisplayString>
     <Expand>
       <ExpandedItem>dictionary_</ExpandedItem>
     </Expand>
   </Type>
   <Type Name="base::ListValue">
     <DisplayString>List ({list_._Mysize} entries)</DisplayString>
     <Expand>
       <ExpandedItem>list_</ExpandedItem>
     </Expand>
   </Type>
 </AutoVisualizer>