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..5900d559d70f3e40a0d39f47b4495ea296e71385 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(
@@ -181,16 +181,19 @@ SpdyPriority ConvertRequestPriorityToSpdyPriority(
     SpdyMajorVersion protocol_version) {
   DCHECK_GE(priority, MINIMUM_PRIORITY);
   DCHECK_LE(priority, MAXIMUM_PRIORITY);
-  return static_cast<SpdyPriority>(MAXIMUM_PRIORITY - priority);
+  return static_cast<SpdyPriority>(MAXIMUM_PRIORITY - priority +
+                                   kV3HighestPriority);
 }
 
 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 - kV3HighestPriority) >
+          (MAXIMUM_PRIORITY - MINIMUM_PRIORITY))
+             ? IDLE
+             : static_cast<RequestPriority>(MAXIMUM_PRIORITY -
+                                            (priority - kV3HighestPriority));
 }
 
 NET_EXPORT_PRIVATE void ConvertHeaderBlockToHttpRequestHeaders(