Bring back the URLLoader from the old Mandoline network service.

content/network/url_loader_unittest.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/files/file_util.h"
+#include "base/message_loop/message_loop.h"
+#include "base/path_service.h"
+#include "base/run_loop.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "content/browser/loader/test_url_loader_client.h"
+#include "content/network/network_context.h"
+#include "content/network/url_loader_impl.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/common/content_paths.h"
+#include "content/public/test/test_browser_thread.h"
+#include "mojo/public/c/system/data_pipe.h"
+#include "mojo/public/cpp/system/wait.h"
+#include "net/test/embedded_test_server/embedded_test_server.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace content {
+
+namespace {
+
+static ResourceRequest CreateResourceRequest(const char* method,
+                                             ResourceType type,
+                                             const GURL& url) {
+  ResourceRequest request;
+  request.method = std::string(method);
+  request.url = url;
+  request.first_party_for_cookies = url;  // bypass third-party cookie blocking
+  request.request_initiator = url::Origin(url);  // ensure initiator is set
+  request.referrer_policy = blink::kWebReferrerPolicyDefault;
+  request.load_flags = 0;
+  request.origin_pid = 0;
+  request.resource_type = type;
+  request.request_context = 0;
+  request.appcache_host_id = kAppCacheNoHostId;
+  request.download_to_file = false;
+  request.should_reset_appcache = false;
+  request.is_main_frame = true;
+  request.parent_is_main_frame = false;
+  request.transition_type = ui::PAGE_TRANSITION_LINK;
+  request.allow_download = true;
+  return request;
+}
+
+std::string ReadData(MojoHandle consumer, size_t size) {
+  CHECK_EQ(mojo::Wait(mojo::Handle(consumer), MOJO_HANDLE_SIGNAL_READABLE),
+           MOJO_RESULT_OK);
+  std::vector<char> buffer(size);
+  uint32_t num_bytes = static_cast<uint32_t>(size);
+  CHECK_EQ(MojoReadData(consumer, buffer.data(), &num_bytes,

[yzshen1, 2017/04/11 21:58:04]

FYI, although this probably always works, there is actually no guarantee that
the data will be available on the first call. The readable signal may be
triggered for partial data, so a ALL_OR_NONE read will result in SHOULD_WAIT in
that case.

Therefore, we should use a while loop to wait and read data until we
successfully read the data out.

[jam, 2017/04/11 22:58:19]

Are you sure how it's used here can fail? Given that everything is running on
the same thread, and it's been flushed before a post task, I figured that it
would be ready by the time this is called. Other unit tests do this as well.

If it's not guaranteed, we will see flakiness and that can be the signal that
it's not working in practice :)

[yzshen1, 2017/04/11 23:22:43]

I am pretty sure that this relies on some undocumented behavior of the Mojo
system API.
Because people find example and copy/paste code, they probably will assume that
this is the right way to do things.

I don't think this test itself matters much though, I will let you decide
whether to leave it as is.

I heard Ken mentioned at some point that he would like to develop some data pipe
utility. Hopefully it will help people to write more robust code.

+                        MOJO_WRITE_DATA_FLAG_ALL_OR_NONE),
+           MOJO_RESULT_OK);
+  CHECK_EQ(num_bytes, static_cast<uint32_t>(size));
+
+  return std::string(buffer.data(), buffer.size());
+}
+
+}  // namespace
+
+class URLLoaderImplTest : public testing::Test {
+ public:
+  URLLoaderImplTest() : io_browser_thread_(BrowserThread::IO, &message_loop_) {}
+  ~URLLoaderImplTest() override {}
+
+  void SetUp() override {
+    test_server_.ServeFilesFromSourceDirectory(
+        base::FilePath(FILE_PATH_LITERAL("content/test/data")));
+    test_server_.Start();
+  }
+
+  void LoadAndCompareFile(const std::string& path) {
+    TestURLLoaderClient client;
+    mojom::URLLoaderPtr loader;
+
+    ResourceRequest request =
+        CreateResourceRequest("GET", RESOURCE_TYPE_MAIN_FRAME,
+                              test_server()->GetURL(std::string("/") + path));
+
+    URLLoaderImpl loader_impl(context(), mojo::MakeRequest(&loader), request,
+                              client.CreateInterfacePtr());
+
+    client.RunUntilComplete();
+
+    base::FilePath file;
+    PathService::Get(content::DIR_TEST_DATA, &file);
+    file = file.AppendASCII(path);
+
+    std::string file_contents;
+    if (!base::ReadFileToString(file, &file_contents)) {
+      ADD_FAILURE() << "File not found: " << file.value();
+      return;
+    }
+
+    std::string data =
+        ReadData(client.response_body().value(), file_contents.size());
+    CHECK_EQ(data, file_contents);
+  }
+
+  net::EmbeddedTestServer* test_server() { return &test_server_; }
+  NetworkContext* context() { return &context_; }
+
+ private:
+  base::MessageLoop message_loop_;
+  TestBrowserThread io_browser_thread_;
+  net::EmbeddedTestServer test_server_;
+  NetworkContext context_;
+};
+
+TEST_F(URLLoaderImplTest, Basic) {
+  LoadAndCompareFile("simple_page.html");
+}
+
+}  // namespace content