Fix #10805 zero dynamic table (#11445) (#11452)

* Fix #10805 zero dynamic table (#11445)

* Added test for #10805 Zero Dynamic Table

* fixed file header

* Added test for #10805 Zero Dynamic Table

* Fix for #10805 Zero Dynamic Table

Set the correct default size for the table.
Always send the max table size on the first encode

* updated file header

Signed-off-by: gregw <gregw@webtide.com>

---------

Signed-off-by: gregw <gregw@webtide.com>

jetty-core/jetty-http2/jetty-http2-hpack/src/main/java/org/eclipse/jetty/http2/hpack/HpackEncoder.java

@@ -99,10 +99,11 @@ public class HpackEncoder
     private int _maxHeaderListSize;
     private int _headerListSize;
     private boolean _validateEncoding = true;
+    private boolean _maxDynamicTableSizeSent = false;
 
     public HpackEncoder()
     {
-        _context = new HpackContext(0);
+        _context = new HpackContext(HpackContext.DEFAULT_MAX_TABLE_CAPACITY);
         _debug = LOG.isDebugEnabled();
         setMaxTableCapacity(HpackContext.DEFAULT_MAX_TABLE_CAPACITY);
         setTableCapacity(HpackContext.DEFAULT_MAX_TABLE_CAPACITY);
@@ -197,8 +198,11 @@ public void encode(ByteBuffer buffer, MetaData metadata) throws HpackException
 
             // If max table size changed, send the correspondent instruction.
             int tableCapacity = getTableCapacity();
-            if (tableCapacity != _context.getMaxDynamicTableSize())
+            if (!_maxDynamicTableSizeSent || tableCapacity != _context.getMaxDynamicTableSize())
+            {
+                _maxDynamicTableSizeSent = true;
                 encodeMaxDynamicTableSize(buffer, tableCapacity);
+            }
 
             // Add Request/response meta fields
             if (metadata.isRequest())