Add a new priority level, THROTTLED, below IDLE.

net/spdy/spdy_http_utils.cc

Index: net/spdy/spdy_http_utils.cc
diff --git a/net/spdy/spdy_http_utils.cc b/net/spdy/spdy_http_utils.cc
index 573bce18b8f893b1ba15fb0fa8c5dd759ea625db..252439f34b9431fde24d0fd6874c3b37f9392db0 100644
--- a/net/spdy/spdy_http_utils.cc
+++ b/net/spdy/spdy_http_utils.cc
@@ -173,7 +173,7 @@ void CreateSpdyHeadersFromHttpResponse(
   }
 }
 
-static_assert(HIGHEST - LOWEST < 4 && HIGHEST - MINIMUM_PRIORITY < 5,
+static_assert(HIGHEST - LOWEST < 4 && HIGHEST - MINIMUM_PRIORITY < 6,
               "request priority incompatible with spdy");
 
 SpdyPriority ConvertRequestPriorityToSpdyPriority(

[mmenke, 2016/05/09 19:25:42]

Need to have the QUIC/SPDY teams weigh in on changing this.

[Randy Smith (Not in Mondays), 2016/05/11 21:30:25]

Ryan, are you willing to play a SPDY expert on TV, since Bence's out?

@@ -188,9 +188,9 @@ NET_EXPORT_PRIVATE RequestPriority ConvertSpdyPriorityToRequestPriority(
     SpdyPriority priority,
     SpdyMajorVersion protocol_version) {
   // Handle invalid values gracefully.
-  // Note that SpdyPriority is not an enum, hence the magic constants.
-  return (priority >= 5) ?
-      IDLE : static_cast<RequestPriority>(4 - priority);
+  return (priority > (MAXIMUM_PRIORITY - MINIMUM_PRIORITY))

[mmenke, 2016/05/09 19:25:42]

This maps IDLE priority to 4, THROTTLED to 5, and THROTTLED+1 to 4?  Why is this
different from the QUIC version?

[Randy Smith (Not in Mondays), 2016/05/11 21:30:25]

Because of ">" rather than ">="?  Because the QUIC version was broken and I
hadn't written tests for it; both now fixed.  

I've also updated this code to be explicit about the relationship to
kV3HighestPriority.

Ryan: Any idea why these are duplicated between SPDY and QUIC?

[Ryan Hamilton, 2016/05/12 22:25:46]

Because QuicPriority != SpdyPriority ... except then it turns out they are the
same. Long story short, it's a wart.

+             ? IDLE
+             : static_cast<RequestPriority>(MAXIMUM_PRIORITY - priority);
 }
 
 NET_EXPORT_PRIVATE void ConvertHeaderBlockToHttpRequestHeaders(