Adding WebContent-free Download

content/browser/download/url_downloader.cc

+// Copyright 2015 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 "content/browser/download/url_downloader.h"
+
+#include "base/location.h"
+#include "base/thread_task_runner_handle.h"
+#include "content/browser/appcache/appcache_interceptor.h"
+#include "content/browser/service_worker/service_worker_request_handler.h"
+#include "content/browser/ssl/ssl_policy.h"
+#include "content/common/ssl_status_serialization.h"
+#include "content/public/browser/cert_store.h"
+#include "content/public/browser/download_save_info.h"
+#include "content/public/browser/signed_certificate_timestamp_store.h"
+#include "content/public/common/process_type.h"
+#include "content/public/common/security_style.h"
+#include "net/base/io_buffer.h"
+#include "net/base/load_flags.h"
+#include "net/base/net_errors.h"
+#include "net/http/http_response_headers.h"
+#include "net/http/http_status_code.h"
+#include "ui/base/page_transition_types.h"
+
+namespace content {
+
+scoped_ptr<UrlDownloader> UrlDownloader::BeginDownload(

[asanka, 2015/12/08 16:58:33]

// static

above this line.

[svaldez, 2015/12/08 20:39:26]

Done.

+    base::WeakPtr<DownloadManagerImpl> download_manager,
+    scoped_ptr<net::URLRequest> request,
+    const Referrer& referrer,
+    bool is_content_initiated,
+    bool prefer_cache,
+    bool do_not_prompt_for_login,
+    scoped_ptr<DownloadSaveInfo> save_info,
+    uint32 download_id,
+    const DownloadUrlParameters::OnStartedCallback& started_callback) {
+  if (!referrer.url.is_valid())
+    request->SetReferrer(std::string());
+  else
+    request->SetReferrer(referrer.url.spec());
+
+  int extra_load_flags = net::LOAD_NORMAL;
+  if (prefer_cache) {
+    // If there is upload data attached, only retrieve from cache because there
+    // is no current mechanism to prompt the user for their consent for a
+    // re-post. For GETs, try to retrieve data from the cache and skip
+    // validating the entry if present.
+    if (request->get_upload() != NULL)
+      extra_load_flags |= net::LOAD_ONLY_FROM_CACHE;
+    else
+      extra_load_flags |= net::LOAD_PREFERRING_CACHE;
+  } else {
+    extra_load_flags |= net::LOAD_DISABLE_CACHE;
+  }
+  request->SetLoadFlags(request->load_flags() | extra_load_flags);
+
+  // We treat a download as a main frame load, and thus update the policy URL on
+  // redirects.
+  //
+  // TODO(davidben): Is this correct? If this came from a
+  // ViewHostMsg_DownloadUrl in a frame, should it have first-party URL set
+  // appropriately?

[asanka, 2015/12/08 16:58:33]

This was done for downloads because we wanted to treat download requests as a
top-level navigation requests. I.e. the request URL at all stages is considered
the first party.

This class doesn't support redirects, so we can just leave the
first_party_url_policy at its default (NEVER_CHANGE_FIRST_PARTY_URL) or whatever
value that the caller has set.

[svaldez, 2015/12/08 20:39:26]

Done.

+  request->set_first_party_url_policy(
+      net::URLRequest::UPDATE_FIRST_PARTY_URL_ON_REDIRECT);
+
+  if (request->url().SchemeIs(url::kBlobScheme))
+    return nullptr;
+
+  scoped_ptr<DownloadRequestCore> handler(new DownloadRequestCore(
+      download_id, request.get(), started_callback, save_info.Pass(),
+      download_manager));
+
+  // From this point forward, the |UrlDownloader| is responsible for
+  // |started_callback|.
+  scoped_ptr<UrlDownloader> downloader(
+      new UrlDownloader(request.Pass(), handler.Pass()));
+
+  downloader->Start();
+
+  return downloader;
+}
+
+UrlDownloader::UrlDownloader(scoped_ptr<net::URLRequest> request,
+                             scoped_ptr<DownloadRequestCore> handler)
+    : request_(request.Pass()),
+      handler_(handler.Pass()),
+      weak_ptr_factory_(this) {}
+
+UrlDownloader::~UrlDownloader() {
+  handler_.reset();
+}
+
+void UrlDownloader::Start() {
+  DCHECK(!request_->is_pending());
+
+  if (!request_->status().is_success()) {

[asanka, 2015/12/08 16:58:33]

Nit: no {

Also, do you know when this would be true?

[svaldez, 2015/12/08 20:39:26]

Requests which are prematurely killed? Copied from ResourceLoader.

+    return;
+  }
+
+  request_->set_delegate(this);
+  request_->Start();
+}
+
+void UrlDownloader::OnReceivedRedirect(net::URLRequest* request,
+                                       const net::RedirectInfo& redirect_info,
+                                       bool* defer_redirect) {
+  DVLOG(1) << "OnReceivedRedirect: " << request_->url().spec();
+  request_->CancelWithError(net::ERR_ABORTED);
+}
+
+void UrlDownloader::OnResponseStarted(net::URLRequest* request) {
+  DVLOG(1) << "OnResponseStarted: " << request_->url().spec();
+
+  if (!request_->status().is_success()) {
+    ResponseCompleted();
+    return;
+  }
+
+  handler_->OnResponseStarted();
+
+  if (request_->status().is_success())

[asanka, 2015/12/08 16:58:33]

I'm guessing you are copying logic in ResourceLoader that assumes that the
request status can change during handler_->OnResponseStarted()?

[svaldez, 2015/12/08 20:39:26]

Acknowledged.

+    StartReading(false);  // Read the first chunk.
+  else
+    ResponseCompleted();
+}
+
+void UrlDownloader::OnReadCompleted(net::URLRequest* request, int bytes_read) {

[asanka, 2015/12/08 16:58:33]

Nit: let's move OnReadCompleted below StartReading(). Logically,
OnReadCompleted() can't be called prior to StartReading() being called.

[svaldez, 2015/12/08 20:39:26]

Done.

+  DVLOG(1) << "OnReadCompleted: \"" << request_->url().spec() << "\""
+           << " bytes_read = " << bytes_read;
+
+  // bytes_read == -1 always implies an error.
+  if (bytes_read == -1 || !request_->status().is_success()) {
+    ResponseCompleted();
+    return;
+  }
+
+  DCHECK(bytes_read >= 0);
+  DCHECK(request_->status().is_success());
+
+  bool defer = false;
+  if (!handler_->OnReadCompleted(bytes_read, &defer)) {
+    request_->CancelWithError(net::ERR_ABORTED);
+    return;
+  }
+  DCHECK(!defer);

[asanka, 2015/12/08 16:58:33]

This is not correct. The ByteStreamWriter can require that the reading be paused
of the downstream ByteStreamReader isn't reading fast enough. If we don't
propagate backpressure, we may end up bloating our read buffers and cause an
unbounded amount of memory to be consumed.

If the ByteStreamWriter signals that the stream be paused, OnReadCompleted()
will set *defer to true, and the loader should pause avoid doing another
OnWillRead/Read/OnReadCompleted cycle until the ByteStream requests that the
stream be resumed. See the corresponding logic in DownloadResourceHandler.

[svaldez, 2015/12/08 20:39:26]

Done.

+
+  if (!request_->status().is_success())
+    return;
+
+  if (bytes_read > 0) {
+    StartReading(true);  // Read the next chunk.
+  } else {
+    // URLRequest reported an EOF. Call ResponseCompleted.
+    DCHECK_EQ(0, bytes_read);
+    ResponseCompleted();
+  }
+}
+
+void UrlDownloader::StartReading(bool is_continuation) {
+  int bytes_read;
+
+  // Make sure we track the buffer in at least one place.  This ensures it gets
+  // deleted even in the case the request has already finished its job and
+  // doesn't use the buffer.
+  scoped_refptr<net::IOBuffer> buf;
+  int buf_size;
+  if (!handler_->OnWillRead(&buf, &buf_size, -1)) {
+    request_->CancelWithError(net::ERR_ABORTED);
+    return;

[asanka, 2015/12/08 16:58:33]

How does OnResponseCompleted() get called in this code path?

[svaldez, 2015/12/08 20:39:26]

Done.

+  }
+
+  DCHECK(buf.get());
+  DCHECK(buf_size > 0);
+
+  request_->Read(buf.get(), buf_size, &bytes_read);
+
+  // If IO is pending, wait for the URLRequest to call OnReadCompleted.
+  if (request_->status().is_io_pending())
+    return;
+
+  if (!is_continuation || bytes_read <= 0) {
+    OnReadCompleted(request_.get(), bytes_read);
+  } else {
+    // Else, trigger OnReadCompleted asynchronously to avoid starving the IO
+    // thread in case the URLRequest can provide data synchronously.
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE,
+        base::Bind(&UrlDownloader::OnReadCompleted,
+                   weak_ptr_factory_.GetWeakPtr(), request_.get(), bytes_read));
+  }
+}
+
+void UrlDownloader::ResponseCompleted() {
+  DVLOG(1) << "ResponseCompleted: " << request_->url().spec();
+
+  handler_->OnResponseCompleted(request_->status());

[asanka, 2015/12/08 16:58:33]

We should discard handler_ after this point since it's no longer useful. Also,
we seem to be making assumptions that the duration of the network request is
tied to the lifetime of the handler.

[svaldez, 2015/12/08 20:39:26]

Done.

+}
+
+}  // namespace content