Remove legacy SourceStream::SourceTypes

The are used in Accept-Encoding handling. The remove legacy types:

SDCH/SDCH_POSSIBLE: Sdch support has since been removed.
GZIP_FALLBACK: This used to be used when sniffing if deflate responses
  might actually be gzipped instead, but is no longer used (I believe we
  removed that logic, though may have just restructured it)
Rejected: I believe this was specifically for when Brotli wasn't
  advertised but we received Brotli responses anyways, to discourage
  sites failing to respect Accept-Encoding advertisements, though it may
  have applied to other schemes. This logic has since been removed. We
  just don't decompress when we see an unadvertised encoding, currently.
Invalid: I'm not sure if this was ever used.

The only histogram that used these enums is Net.ContentDecodingFailed2,
which expired and was removed in https://crbug.com/969974

Bug: NONE
Change-Id: Id6968b8de8254e065ad57eb7a0fdb35d600c64dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2716903
Reviewed-by: Alex Rudenko <alexrudenko@chromium.org>
Reviewed-by: Maksim Orlovich <morlovich@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#857189}

net/BUILD.gn

@@ -660,7 +660,6 @@ component("net") {
       "filter/gzip_source_stream.h",
       "filter/source_stream.cc",
       "filter/source_stream.h",
-      "filter/source_stream_type_list.h",
       "http/alternative_service.cc",
       "http/alternative_service.h",
       "http/bidirectional_stream.cc",

net/filter/source_stream.h

@@ -22,11 +22,11 @@ class IOBuffer;
 class NET_EXPORT_PRIVATE SourceStream {
  public:
   enum SourceType {
-#define SOURCE_STREAM_TYPE(label) TYPE_##label,
-#include "net/filter/source_stream_type_list.h"
-#undef SOURCE_STREAM_TYPE
-    // Used for UMA.
-    TYPE_MAX,
+    TYPE_BROTLI,
+    TYPE_DEFLATE,
+    TYPE_GZIP,
+    TYPE_UNKNOWN,
+    TYPE_NONE,
   };
 
   // |type| is the type of the SourceStream.

net/url_request/url_request_http_job.cc

@@ -1115,14 +1115,6 @@ std::unique_ptr<SourceStream> URLRequestHttpJob::SetUpSourceStream() {
         // Request will not be canceled; though
         // it is expected that user will see malformed / garbage response.
         return upstream;
-      case SourceStream::TYPE_GZIP_FALLBACK_DEPRECATED:
-      case SourceStream::TYPE_SDCH_DEPRECATED:
-      case SourceStream::TYPE_SDCH_POSSIBLE_DEPRECATED:
-      case SourceStream::TYPE_REJECTED:
-      case SourceStream::TYPE_INVALID:
-      case SourceStream::TYPE_MAX:
-        NOTREACHED();
-        return nullptr;
     }
   }
 
@@ -1137,14 +1129,8 @@ std::unique_ptr<SourceStream> URLRequestHttpJob::SetUpSourceStream() {
       case SourceStream::TYPE_DEFLATE:
         downstream = GzipSourceStream::Create(std::move(upstream), type);
         break;
-      case SourceStream::TYPE_GZIP_FALLBACK_DEPRECATED:
-      case SourceStream::TYPE_SDCH_DEPRECATED:
-      case SourceStream::TYPE_SDCH_POSSIBLE_DEPRECATED:
       case SourceStream::TYPE_NONE:
-      case SourceStream::TYPE_INVALID:
-      case SourceStream::TYPE_REJECTED:
       case SourceStream::TYPE_UNKNOWN:
-      case SourceStream::TYPE_MAX:
         NOTREACHED();
         return nullptr;
     }