Use enum for accept_range field

"Accept-Ranges" header are not required for servers supporting range
requests. This CL changes the accept_range field in DownloadCreateInfo
to use an enum so that we can experiment parallel download even if
range support is unsure.

BUG=917366

Change-Id: I9d6d444437650957b12225da0cada85d0cce5473
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1645480Reviewed-by: Min Qin <qinmin@chromium.org>
Reviewed-by: Xing Liu <xingliu@chromium.org>
Commit-Queue: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666527}

components/download/internal/common/download_create_info.cc

@@ -28,7 +28,7 @@ DownloadCreateInfo::DownloadCreateInfo(
       save_info(std::move(save_info)),
       render_process_id(-1),
       render_frame_id(-1),
-      accept_range(false),
+      accept_range(RangeRequestSupportType::kNoSupport),
       connection_info(net::HttpResponseInfo::CONNECTION_INFO_UNKNOWN),
       method("GET"),
       ukm_source_id(ukm::kInvalidSourceId) {}

components/download/internal/common/download_job_factory.cc

@@ -47,10 +47,11 @@ bool IsParallelizableDownload(const DownloadCreateInfo& create_info,
       create_info.method == "GET" && create_info.url().SchemeIsHTTPOrHTTPS();
   bool partial_response_success =
       download_item->GetReceivedSlices().empty() || create_info.offset != 0;
-  bool is_parallelizable = has_strong_validator && create_info.accept_range &&
-                           has_content_length && satisfy_min_file_size &&
-                           satisfy_connection_type && http_get_method &&
-                           partial_response_success;
+  bool is_parallelizable =
+      has_strong_validator &&
+      create_info.accept_range == RangeRequestSupportType::kSupport &&
+      has_content_length && satisfy_min_file_size && satisfy_connection_type &&
+      http_get_method && partial_response_success;
 
   if (!IsParallelDownloadEnabled())
     return is_parallelizable;
@@ -64,7 +65,7 @@ bool IsParallelizableDownload(const DownloadCreateInfo& create_info,
     RecordParallelDownloadCreationEvent(
         ParallelDownloadCreationEvent::FALLBACK_REASON_STRONG_VALIDATORS);
   }
-  if (!create_info.accept_range) {
+  if (create_info.accept_range != RangeRequestSupportType::kSupport) {
     RecordParallelDownloadCreationEvent(
         ParallelDownloadCreationEvent::FALLBACK_REASON_ACCEPT_RANGE_HEADER);
   }

components/download/internal/common/download_utils.cc

@@ -237,10 +237,15 @@ void HandleResponseHeaders(const net::HttpResponseHeaders* headers,
   // In RFC 7233, a single part 206 partial response must generate
   // Content-Range. Accept-Range may be sent in 200 response to indicate the
   // server can handle range request, but optional in 206 response.
-  create_info->accept_range =
-      headers->HasHeaderValue("Accept-Ranges", "bytes") ||
+  if (headers->HasHeaderValue("Accept-Ranges", "bytes") ||
       (headers->HasHeader("Content-Range") &&
-       headers->response_code() == net::HTTP_PARTIAL_CONTENT);
+       headers->response_code() == net::HTTP_PARTIAL_CONTENT)) {
+    create_info->accept_range = RangeRequestSupportType::kSupport;
+  } else if (headers->HasHeaderValue("Accept-Ranges", "none")) {
+    create_info->accept_range = RangeRequestSupportType::kNoSupport;
+  } else {
+    create_info->accept_range = RangeRequestSupportType::kUnknown;
+  }
 }
 
 std::unique_ptr<network::ResourceRequest> CreateResourceRequest(

components/download/public/common/download_create_info.h

@@ -35,6 +35,16 @@ class HttpResponseHeaders;
 
 namespace download {
 
+// Server support for range request inferred from the response headers.
+// |kSupport| value means the server supports range requests. |kNoSupport|
+// means no range request is accepted by server. and |kUnknown| is used if
+// range request support cannot be inferred from response headers.
+enum class RangeRequestSupportType {
+  kSupport = 0,
+  kUnknown,
+  kNoSupport,
+};
+
 // Used for informing the download manager of a new download, since we don't
 // want to pass |DownloadItem|s between threads.
 struct COMPONENTS_DOWNLOAD_EXPORT DownloadCreateInfo {
@@ -142,10 +152,8 @@ struct COMPONENTS_DOWNLOAD_EXPORT DownloadCreateInfo {
   // For continuing a download, the ETag of the file.
   std::string etag;
 
-  // If the download response can be partial content.
-  // Either "Accept-Ranges" or "Content-Range" header presents in the
-  // response header.
-  bool accept_range;
+  // Whether the server supports range requests.
+  RangeRequestSupportType accept_range;
 
   // The HTTP connection type.
   net::HttpResponseInfo::ConnectionInfo connection_info;