[web_engine] Handle ranged HTTP GET from fuchsia-dir:// resources.

Parses and properly handles values given to the "Range" HTTP request
header.

Fixes an issue which was preventing the playback of media files, which
stream their input from at least one GET request.

Test: playback of large media file now works well (Big Buck Bunny).
Bug: 1018917
Change-Id: Ie09ab51485114bdb4d82aae6268f4dce4230f201
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1884574Reviewed-by: David Dorwin <ddorwin@chromium.org>
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710927}

fuchsia/engine/browser/content_directory_loader_factory.cc

@@ -29,6 +29,8 @@
 #include "net/base/filename_util.h"
 #include "net/base/mime_sniffer.h"
 #include "net/base/parse_number.h"
+#include "net/http/http_byte_range.h"
+#include "net/http/http_util.h"
 #include "services/network/public/mojom/url_loader.mojom.h"
 #include "services/network/public/mojom/url_response_head.mojom.h"
 
@@ -111,6 +113,38 @@ scoped_refptr<net::HttpResponseHeaders> CreateHeaders(
   return headers;
 }
 
+// Determines which range of bytes should be sent in the response.
+// If a range is specified in |headers|, then |start| and |length| are set to
+// the range's boundaries and the function returns true.
+// If no range is specified in |headers|, then the entire range [0,
+// |max_length|) is set and the function returns true.
+// If the requested range is invalid, then the function returns false.
+bool GetRangeForRequest(const net::HttpRequestHeaders& headers,
+                        size_t max_length,
+                        size_t* start,
+                        size_t* length) {
+  std::string range_header;
+  net::HttpByteRange byte_range;
+  if (headers.GetHeader(net::HttpRequestHeaders::kRange, &range_header)) {
+    std::vector<net::HttpByteRange> ranges;
+    if (net::HttpUtil::ParseRangeHeader(range_header, &ranges) &&
+        ranges.size() == 1) {
+      byte_range = ranges[0];
+    } else {
+      // Only one range is allowed.
+      return false;
+    }
+  }
+  if (!byte_range.ComputeBounds(max_length)) {
+    return false;
+  }
+
+  *start = byte_range.first_byte_position();
+  *length =
+      byte_range.last_byte_position() - byte_range.first_byte_position() + 1;
+  return true;
+}
+
 // Copies data from a fuchsia.io.Node file into a URL response stream.
 class ContentDirectoryURLLoader : public network::mojom::URLLoader {
  public:
@@ -208,9 +242,19 @@ class ContentDirectoryURLLoader : public network::mojom::URLLoader {
           reinterpret_cast<char*>(mmap_.data()), mmap_.length(), request.url,
           "", net::ForceSniffFileUrlsForHtml::kDisabled, &*mime_type);
     }
+
+    size_t start_offset;
+    size_t content_length;
+    if (!GetRangeForRequest(request.headers, mmap_.length(), &start_offset,
+                            &content_length)) {
+      client_->OnComplete(network::URLLoaderCompletionStatus(
+          net::ERR_REQUEST_RANGE_NOT_SATISFIABLE));
+      return;
+    }
+
     response->mime_type = *mime_type;
     response->headers = CreateHeaders(*mime_type, charset);
-    response->content_length = mmap_.length();
+    response->content_length = content_length;
     client_->OnReceiveResponse(std::move(response));
 
     // Set up the Mojo DataPipe used for streaming the response payload to the
@@ -231,8 +275,9 @@ class ContentDirectoryURLLoader : public network::mojom::URLLoader {
         std::make_unique<mojo::DataPipeProducer>(std::move(producer_handle));
     body_writer_->Write(
         std::make_unique<mojo::StringDataSource>(
-            base::StringPiece(reinterpret_cast<char*>(mmap_.data()),
-                              mmap_.length()),
+            base::StringPiece(
+                reinterpret_cast<char*>(mmap_.data() + start_offset),
+                content_length),
             mojo::StringDataSource::AsyncWritingMode::
                 STRING_STAYS_VALID_UNTIL_COMPLETION),
         base::BindOnce(&ContentDirectoryURLLoader::OnWriteComplete,