[#1422] ReadOnlyByteBuffer.isWritable() should return false

buffer/src/main/java/io/netty/buffer/ReadOnlyByteBuf.java

@@ -44,6 +44,16 @@ public class ReadOnlyByteBuf extends AbstractDerivedByteBuf {
         setIndex(buffer.readerIndex(), buffer.writerIndex());
     }
 
+    @Override
+    public boolean isWritable() {
+        return false;
+    }
+
+    @Override
+    public boolean isWritable(int numBytes) {
+        return false;
+    }
+
     @Override
     public ByteBuf unwrap() {
         return buffer;

buffer/src/test/java/io/netty/buffer/ReadOnlyByteBufTest.java

@@ -174,4 +174,12 @@ public class ReadOnlyByteBufTest {
     public void shouldRejectSetBytes5() {
         unmodifiableBuffer(EMPTY_BUFFER).setBytes(0, (ByteBuffer) null);
     }
+
+    public void shouldIndicateNotWriteable() {
+        assertFalse(unmodifiableBuffer(buffer(1)).isWritable());
+    }
+
+    public void shouldIndicteNotWritableAnyNumber() {
+        assertFalse(unmodifiableBuffer(buffer(1)).isWritable(1));
+    }
 }