Expand set of known header names and values (#117989)

* Collection expressions for known values

* Simplify new()

* Expand set of known header names and values

* Also add text/plain without a space

Author: MihaZupan

src/libraries/System.Net.Http/src/System/Net/Http/Headers/HeaderDescriptor.cs

@@ -207,19 +207,25 @@ public string GetHeaderValue(ReadOnlySpan<byte> headerValue, Encoding? valueEnco
                     break;
 
                 case 10:
-                    switch (contentTypeValue[0])
+                    switch (contentTypeValue[6])
                     {
-                        case (byte)'t': candidate = "text/plain"; break; // [t]ext/plain
-                        case (byte)'i': candidate = "image/jpeg"; break; // [i]mage/jpeg
+                        case (byte)'l': candidate = "text/plain"; break; // text/p[l]ain
+                        case (byte)'j': candidate = "image/jpeg"; break; // image/[j]peg
+                        case (byte)'w': candidate = "image/webp"; break; // image/[w]ebp
                     }
                     break;
 
+                case 13:
+                    candidate = "image/svg+xml"; // image/svg+xml
+                    break;
+
                 case 15:
                     switch (contentTypeValue[12])
                     {
                         case (byte)'p': candidate = "application/pdf"; break; // application/[p]df
                         case (byte)'x': candidate = "application/xml"; break; // application/[x]ml
                         case (byte)'z': candidate = "application/zip"; break; // application/[z]ip
+                        case (byte)'i': candidate = "text/javascript"; break; // text/javascr[i]pt
                     }
                     break;
 
@@ -231,6 +237,10 @@ public string GetHeaderValue(ReadOnlySpan<byte> headerValue, Encoding? valueEnco
                     }
                     break;
 
+                case 17:
+                    candidate = "text/event-stream"; // text/event-stream
+                    break;
+
                 case 19:
                     candidate = "multipart/form-data"; // multipart/form-data
                     break;
@@ -239,17 +249,47 @@ public string GetHeaderValue(ReadOnlySpan<byte> headerValue, Encoding? valueEnco
                     candidate = "application/javascript"; // application/javascript
                     break;
 
+                case 23:
+                    switch (contentTypeValue[18])
+                    {
+                        case (byte)'u': candidate = "text/html;charset=utf-8"; break; // text/html;charset=[u]tf-8
+                        case (byte)'U': candidate = "text/html;charset=UTF-8"; break; // text/html;charset=[U]TF-8
+                    }
+                    break;
+
                 case 24:
-                    switch (contentTypeValue[19])
+                    switch (contentTypeValue[10] ^ contentTypeValue[19])
                     {
-                        case (byte)'t': candidate = "application/octet-stream"; break; // application/octet-s[t]ream
-                        case (byte)'u': candidate = "text/html; charset=utf-8"; break; // text/html; charset=[u]tf-8
-                        case (byte)'U': candidate = "text/html; charset=UTF-8"; break; // text/html; charset=[U]TF-8
+                        case 'n' ^ 't': candidate = "application/octet-stream"; break; // applicatio[n]/octet-s[t]ream
+                        case ' ' ^ 'u': candidate = "text/html; charset=utf-8"; break; // text/html;[ ]charset=[u]tf-8
+                        case ' ' ^ 'U': candidate = "text/html; charset=UTF-8"; break; // text/html;[ ]charset=[U]TF-8
+                        case ';' ^ 'u': candidate = "text/plain;charset=utf-8"; break; // text/plain[;]charset=[u]tf-8
+                        case ';' ^ 'U': candidate = "text/plain;charset=UTF-8"; break; // text/plain[;]charset=[U]TF-8
                     }
                     break;
 
                 case 25:
-                    candidate = "text/plain; charset=utf-8"; // text/plain; charset=utf-8
+                    switch (contentTypeValue[20])
+                    {
+                        case (byte)'u': candidate = "text/plain; charset=utf-8"; break; // text/plain; charset=[u]tf-8
+                        case (byte)'U': candidate = "text/plain; charset=UTF-8"; break; // text/plain; charset=[U]TF-8
+                    }
+                    break;
+
+                case 29:
+                    switch (contentTypeValue[19])
+                    {
+                        case (byte)'I': candidate = "text/html; charset=ISO-8859-1"; break; // text/html; charset=[I]SO-8859-1
+                        case (byte)'i': candidate = "text/html; charset=iso-8859-1"; break; // text/html; charset=[i]so-8859-1
+                    }
+                    break;
+
+                case 30:
+                    switch (contentTypeValue[25])
+                    {
+                        case (byte)'u': candidate = "text/javascript; charset=utf-8"; break; // text/javascript; charset=[u]tf-8
+                        case (byte)'U': candidate = "text/javascript; charset=UTF-8"; break; // text/javascript; charset=[U]TF-8
+                    }
                     break;
 
                 case 31:

src/libraries/System.Net.Http/src/System/Net/Http/Headers/KnownHeader.cs

@@ -8,12 +8,9 @@ namespace System.Net.Http.Headers
 {
     internal sealed partial class KnownHeader
     {
-        public KnownHeader(string name, int? http2StaticTableIndex = null, int? http3StaticTableIndex = null) :
-            this(name, HttpHeaderType.Custom, parser: null, knownValues: null, http2StaticTableIndex, http3StaticTableIndex)
-        {
-            Debug.Assert(!string.IsNullOrEmpty(name));
-            Debug.Assert(name[0] == ':' || HttpRuleParser.IsToken(name));
-        }
+        public KnownHeader(string name, string[]? knownValues = null, int? http2StaticTableIndex = null, int? http3StaticTableIndex = null)
+            : this(name, HttpHeaderType.Custom, parser: null, knownValues, http2StaticTableIndex, http3StaticTableIndex)
+        { }
 
         public KnownHeader(string name, HttpHeaderType headerType, HttpHeaderParser? parser, string[]? knownValues = null, int? http2StaticTableIndex = null, int? http3StaticTableIndex = null)
         {