Remove renumbering indirection in settings frames (#8385)

This makes the code difficult to understand.

Co-authored-by: Jesse Wilson <[email protected]>
Co-authored-by: Yuri Schimke <[email protected]>

Author: swankjesse

okhttp/src/main/kotlin/okhttp3/internal/http2/Http2Reader.kt

@@ -261,7 +261,7 @@ class Http2Reader(
     if (length % 6 != 0) throw IOException("TYPE_SETTINGS length % 6 != 0: $length")
     val settings = Settings()
     for (i in 0 until length step 6) {
-      var id = source.readShort() and 0xffff
+      val id = source.readShort() and 0xffff
       val value = source.readInt()
 
       when (id) {
@@ -277,11 +277,11 @@ class Http2Reader(
         }
 
         // SETTINGS_MAX_CONCURRENT_STREAMS
-        3 -> id = 4 // Renumbered in draft 10.
+        3 -> {
+        }
 
         // SETTINGS_INITIAL_WINDOW_SIZE
         4 -> {
-          id = 7 // Renumbered in draft 10.
           if (value < 0) {
             throw IOException("PROTOCOL_ERROR SETTINGS_INITIAL_WINDOW_SIZE > 2^31 - 1")
           }

okhttp/src/main/kotlin/okhttp3/internal/http2/Http2Writer.kt

@@ -209,13 +209,7 @@ class Http2Writer(
       )
       for (i in 0 until Settings.COUNT) {
         if (!settings.isSet(i)) continue
-        val id =
-          when (i) {
-            4 -> 3 // SETTINGS_MAX_CONCURRENT_STREAMS renumbered.
-            7 -> 4 // SETTINGS_INITIAL_WINDOW_SIZE renumbered.
-            else -> i
-          }
-        sink.writeShort(id)
+        sink.writeShort(i)
         sink.writeInt(settings[i])
       }
       sink.flush()

okhttp/src/main/kotlin/okhttp3/internal/http2/Settings.kt

@@ -116,17 +116,17 @@ class Settings {
     const val ENABLE_PUSH = 2
 
     /** Sender's maximum number of concurrent streams. */
-    const val MAX_CONCURRENT_STREAMS = 4
+    const val MAX_CONCURRENT_STREAMS = 3
+
+    /** Window size in bytes. */
+    const val INITIAL_WINDOW_SIZE = 4
 
     /** HTTP/2: Size in bytes of the largest frame payload the sender will accept. */
     const val MAX_FRAME_SIZE = 5
 
     /** HTTP/2: Advisory only. Size in bytes of the largest header list the sender will accept. */
     const val MAX_HEADER_LIST_SIZE = 6
 
-    /** Window size in bytes. */
-    const val INITIAL_WINDOW_SIZE = 7
-
     /** Total number of settings. */
     const val COUNT = 10
   }