Avoid overflow on left shift in HpackVarintDecoder::Resume().

net/http2/hpack/decoder/hpack_varint_decoder.h

Index: net/http2/hpack/decoder/hpack_varint_decoder.h
diff --git a/net/http2/hpack/decoder/hpack_varint_decoder.h b/net/http2/hpack/decoder/hpack_varint_decoder.h
index b110fad23a983b40b0e7974e56bd43ca9bbf56e1..21d230371a56e94afc43b04f400e245ae44e9f4f 100644
--- a/net/http2/hpack/decoder/hpack_varint_decoder.h
+++ b/net/http2/hpack/decoder/hpack_varint_decoder.h
@@ -95,13 +95,12 @@ class NET_EXPORT_PRIVATE HpackVarintDecoder {
         return DecodeStatus::kDecodeInProgress;
       }
       uint8_t byte = db->DecodeUInt8();
+      if (offset_ == MaxOffset() && byte != 0)

[xunjieli, 2017/04/17 20:51:34]

Can we change this to a while-loop to be more readable? It's hard to know what's
going on in this if-conditional.


    while (offset_ <= std::min(MaxOffset(), sizeof(value_) - sizeof(uint8))) {
      if (db->Empty()) {
        return DecodeStatus::kDecodeInProgress;
      }
      uint8_t byte = db->DecodeUInt8();
      value_ += (byte & 0x7f) << offset_;
      if ((byte & 0x80) == 0) {
          MarkDone();
          return DecodeStatus::kDecodeDone;
      }
      offset_ += 7;
    }

+        break;
       value_ += (byte & 0x7f) << offset_;
       if ((byte & 0x80) == 0) {
-        if (offset_ < MaxOffset() || byte == 0) {
-          MarkDone();
-          return DecodeStatus::kDecodeDone;
-        }
-        break;
+        MarkDone();
+        return DecodeStatus::kDecodeDone;
       }
       offset_ += 7;
     } while (offset_ <= MaxOffset());