StringView: Make it easy to construct from a ByteBuffer.

AK/StringView.cpp

@@ -10,6 +10,12 @@ StringView::StringView(const String& string)
 {
 }
 
+StringView::StringView(const ByteBuffer& buffer)
+    : m_characters((const char*)buffer.data())
+    , m_length(buffer.size())
+{
+}
+
 Vector<StringView> StringView::split_view(const char separator) const
 {
     if (is_empty())

AK/StringView.h

@@ -4,6 +4,7 @@
 
 namespace AK {
 
+class ByteBuffer;
 class String;
 class StringImpl;
 
@@ -28,7 +29,9 @@ public:
                 ++m_length;
         }
     }
-    StringView(const String& string);
+
+    StringView(const ByteBuffer&);
+    StringView(const String&);
 
     bool is_null() const { return !m_characters; }
     bool is_empty() const { return m_length == 0; }