Deprecate HTTP/2 PAD_HIGH field and enforce max padding size to 256 octets.

net/spdy/spdy_protocol.cc

Index: net/spdy/spdy_protocol.cc
diff --git a/net/spdy/spdy_protocol.cc b/net/spdy/spdy_protocol.cc
index 68b3e0f8c2f32bae05fd688cb91034cca5342924..fd435122f6485d5397f721aee2c63c5b946bebe2 100644
--- a/net/spdy/spdy_protocol.cc
+++ b/net/spdy/spdy_protocol.cc
@@ -13,16 +13,14 @@ SpdyFrameWithNameValueBlockIR::~SpdyFrameWithNameValueBlockIR() {}
 
 SpdyDataIR::SpdyDataIR(SpdyStreamId stream_id, const base::StringPiece& data)
     : SpdyFrameWithFinIR(stream_id),
-      pad_low_(false),
-      pad_high_(false),
+      padded_(false),
       padding_payload_len_(0) {
   SetDataDeep(data);
 }
 
 SpdyDataIR::SpdyDataIR(SpdyStreamId stream_id)
     : SpdyFrameWithFinIR(stream_id),
-      pad_low_(false),
-      pad_high_(false),
+      padded_(false),
       padding_payload_len_(0) {}
 
 SpdyDataIR::~SpdyDataIR() {}