AK: Tweak ShortString bit layout slightly

Move the byte count one step to the left in order to make space
for the JS::StringOrSymbol flag.

Author: awesomekling

AK/StringBase.cpp

@@ -18,7 +18,7 @@ ReadonlyBytes ShortString::bytes() const
 
 size_t ShortString::byte_count() const
 {
-    return byte_count_and_short_string_flag >> 1;
+    return byte_count_and_short_string_flag >> StringBase::SHORT_STRING_BYTE_COUNT_SHIFT_COUNT;
 }
 
 StringBase::StringBase(NonnullRefPtr<Detail::StringData const> data)
@@ -78,7 +78,7 @@ size_t StringBase::byte_count() const
 {
     ASSERT(!is_invalid());
     if (is_short_string())
-        return m_short_string.byte_count_and_short_string_flag >> 1;
+        return m_short_string.byte_count_and_short_string_flag >> StringBase::SHORT_STRING_BYTE_COUNT_SHIFT_COUNT;
     return m_data->byte_count();
 }
 

AK/StringBase.h

@@ -103,9 +103,11 @@ class StringBase {
 private:
     friend class ::AK::String;
     friend class ::AK::FlyString;
+    friend struct ::AK::Detail::ShortString;
 
     // NOTE: If the least significant bit of the pointer is set, this is a short string.
     static constexpr uintptr_t SHORT_STRING_FLAG = 1;
+    static constexpr unsigned SHORT_STRING_BYTE_COUNT_SHIFT_COUNT = 2;
 
     explicit StringBase(NonnullRefPtr<Detail::StringData const>);
 
@@ -127,7 +129,7 @@ class StringBase {
         VERIFY(byte_count <= MAX_SHORT_STRING_BYTE_COUNT);
 
         m_short_string = ShortString {};
-        m_short_string.byte_count_and_short_string_flag = (byte_count << 1) | SHORT_STRING_FLAG;
+        m_short_string.byte_count_and_short_string_flag = (byte_count << SHORT_STRING_BYTE_COUNT_SHIFT_COUNT) | SHORT_STRING_FLAG;
         return { m_short_string.storage, byte_count };
     }