Client Hints

Client Hints can be used as input to proactive content negotiation;
just as the Accept header allowed clients to indicate what formats
they prefer, Client Hints allow clients to indicate a list of device
and agent specific preferences.

See:
https://github.com/igrigorik/http-client-hints/blob/draft2/draft-grigorik-http-client-hints-01.txt

Patched from https://codereview.chromium.org/23654014/, which was
patched from https://codereview.chromium.org/11970002

BUG=170388
CONTRIBUTOR=yoav@yoav.ws

Review URL: https://codereview.chromium.org/24451003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225425 0039d316-1c4b-4281-b951-d872f2087c98

12 files changed, 194 insertions, 0 deletions

diff --git a/AUTHORS b/AUTHORS
index a7cc2ae..fe98bcf 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -285,6 +285,7 @@ Yael Aharon <yael.aharon@intel.com>
 Yair Yogev <progame@chromium.org>
 Yang Gu <yang.gu@intel.com>
 Yarin Kaul <yarin.kaul@gmail.com>
+Yoav Weiss <yoav@yoav.ws>
 Yoav Zilberberg <yoav.zilberberg@gmail.com>
 Yong Shin <sy3620@gmail.com>
 Yongsheng Zhu <yongsheng.zhu@intel.com>
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 13f71ce..ccad1f5 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -511,6 +511,8 @@ void IOThread::InitAsync() {
   ChromeNetworkDelegate* network_delegate =
       new ChromeNetworkDelegate(extension_event_router_forwarder_,
                                 &system_enable_referrers_);
+  if (command_line.HasSwitch(switches::kEnableClientHints))
+    network_delegate->SetEnableClientHints();
   if (command_line.HasSwitch(switches::kDisableExtensionsHttpThrottling))
     network_delegate->NeverThrottleRequests();
   globals_->system_network_delegate.reset(network_delegate);
diff --git a/chrome/browser/net/chrome_network_delegate.cc b/chrome/browser/net/chrome_network_delegate.cc
index 11a211f..6ecac3d 100644
--- a/chrome/browser/net/chrome_network_delegate.cc
+++ b/chrome/browser/net/chrome_network_delegate.cc
@@ -30,6 +30,7 @@
 #include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/google/google_util.h"
 #include "chrome/browser/net/chrome_network_data_saving_metrics.h"
+#include "chrome/browser/net/client_hints.h"
 #include "chrome/browser/net/connect_interceptor.h"
 #include "chrome/browser/net/load_time_stats.h"
 #include "chrome/browser/performance_monitor/performance_monitor.h"
@@ -334,6 +335,11 @@ void ChromeNetworkDelegate::set_predictor(
       new chrome_browser_net::ConnectInterceptor(predictor));
 }
 
+void ChromeNetworkDelegate::SetEnableClientHints() {
+  client_hints_.reset(new ClientHints());
+  client_hints_->Init();
+}
+
 // static
 void ChromeNetworkDelegate::NeverThrottleRequests() {
   g_never_throttle_requests_ = true;
@@ -418,6 +424,12 @@ int ChromeNetworkDelegate::OnBeforeURLRequest(
   if (enable_do_not_track_ && enable_do_not_track_->GetValue())
     request->SetExtraRequestHeaderByName(kDNTHeader, "1", true /* override */);
 
+  if (client_hints_) {
+    request->SetExtraRequestHeaderByName(
+        ClientHints::kDevicePixelRatioHeader,
+        client_hints_->GetDevicePixelRatioHeader(), true);
+  }
+
   bool force_safe_search = force_google_safe_search_ &&
                            force_google_safe_search_->GetValue();
 
diff --git a/chrome/browser/net/chrome_network_delegate.h b/chrome/browser/net/chrome_network_delegate.h
index e9bf978..ea5ddbb 100644
--- a/chrome/browser/net/chrome_network_delegate.h
+++ b/chrome/browser/net/chrome_network_delegate.h
@@ -10,9 +10,11 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/values.h"
 #include "net/base/network_delegate.h"
 
+class ClientHints;
 class CookieSettings;
 class ExtensionInfoMap;
 class PrefService;
@@ -90,6 +92,9 @@ class ChromeNetworkDelegate : public net::NetworkDelegate {
     force_google_safe_search_ = force_google_safe_search;
   }
 
+  // Adds the Client Hints header to HTTP requests.
+  void SetEnableClientHints();
+
   // Causes |OnCanThrottleRequest| to always return false, for all
   // instances of this object.
   static void NeverThrottleRequests();
@@ -207,6 +212,8 @@ class ChromeNetworkDelegate : public net::NetworkDelegate {
   // Total original size of all content before it was transferred.
   int64 original_content_length_;
 
+  scoped_ptr<ClientHints> client_hints_;
+
   DISALLOW_COPY_AND_ASSIGN(ChromeNetworkDelegate);
 };
 
diff --git a/chrome/browser/net/client_hints.cc b/chrome/browser/net/client_hints.cc
new file mode 100644
index 0000000..af22726
--- /dev/null
+++ b/chrome/browser/net/client_hints.cc
@@ -0,0 +1,70 @@
+// Copyright 2013 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 "chrome/browser/net/client_hints.h"
+
+#include <locale>
+
+#include "base/bind.h"
+#include "base/strings/stringprintf.h"
+#include "base/task_runner_util.h"
+#include "content/public/browser/browser_thread.h"
+#include "ui/gfx/screen.h"
+
+namespace {
+
+float FetchScreenInfoOnUIThread() {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  // TODO(bengr): Consider multi-display scenarios.
+  gfx::Display display = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
+  return display.device_scale_factor();
+}
+
+}  // namespace
+
+const char ClientHints::kDevicePixelRatioHeader[] = "CH-DPR";
+
+ClientHints::ClientHints()
+    : weak_ptr_factory_(this) {
+}
+
+ClientHints::~ClientHints() {
+}
+
+void ClientHints::Init() {
+  // TODO(bengr): Observe the device pixel ratio in case it changes during
+  // the Chrome session.
+  RetrieveScreenInfo();
+}
+
+bool ClientHints::RetrieveScreenInfo() {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
+  return content::BrowserThread::PostTaskAndReplyWithResult(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&FetchScreenInfoOnUIThread),
+      base::Bind(
+          &ClientHints::UpdateScreenInfo, weak_ptr_factory_.GetWeakPtr()));
+}
+
+const std::string& ClientHints::GetDevicePixelRatioHeader() const {
+  return screen_hints_;
+}
+
+void ClientHints::UpdateScreenInfo(float device_pixel_ratio_value) {
+  if (device_pixel_ratio_value <= 0.0)
+    return;
+  std::string device_pixel_ratio = base::StringPrintf("%.2f",
+      device_pixel_ratio_value);
+  // Make sure the Client Hints value doesn't change
+  // according to the machine's locale
+  std::locale locale;
+  for (std::string::iterator it = device_pixel_ratio.begin();
+       it != device_pixel_ratio.end(); ++it) {
+    if (!std::isdigit(*it, locale))
+      *it = '.';
+  }
+  screen_hints_ = device_pixel_ratio;
+}
+
diff --git a/chrome/browser/net/client_hints.h b/chrome/browser/net/client_hints.h
new file mode 100644
index 0000000..c4beb39
--- /dev/null
+++ b/chrome/browser/net/client_hints.h
@@ -0,0 +1,44 @@
+// Copyright 2013 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.
+
+#ifndef CHROME_BROWSER_NET_CLIENT_HINTS_H_
+#define CHROME_BROWSER_NET_CLIENT_HINTS_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/weak_ptr.h"
+
+// ClientHints is a repository in Chrome for information used
+// to create the Client-Hints request header. For more information, see:
+// https://github.com/igrigorik/http-client-hints/blob/draft2/draft-grigorik-http-client-hints-01.txt
+class ClientHints {
+ public:
+  static const char kDevicePixelRatioHeader[];
+
+  ClientHints();
+  ~ClientHints();
+
+  void Init();
+
+  // Returns the device pixel ratio as a string.  Its value is the same as
+  // window.devicePixelRatio in Javascript.
+  const std::string& GetDevicePixelRatioHeader() const;
+
+ private:
+  friend class ClientHintsTest;
+
+  // Retrieves and updates screen information for use on the IO thread.
+  bool RetrieveScreenInfo();
+
+  void UpdateScreenInfo(float device_pixel_ratio_value);
+
+  std::string screen_hints_;
+
+  base::WeakPtrFactory<ClientHints> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ClientHints);
+};
+
+#endif  // CHROME_BROWSER_NET_CLIENT_HINTS_H_
diff --git a/chrome/browser/net/client_hints_unittest.cc b/chrome/browser/net/client_hints_unittest.cc
new file mode 100644
index 0000000..c93b3b6
--- /dev/null
+++ b/chrome/browser/net/client_hints_unittest.cc
@@ -0,0 +1,49 @@
+// Copyright 2013 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 "chrome/browser/net/client_hints.h"
+
+#include <locale.h>
+
+#include "base/logging.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+class ClientHintsTest : public testing::Test {
+ public:
+  void UpdateScreenInfo(float pixel_ratio) {
+    client_hints_.UpdateScreenInfo(pixel_ratio);
+  };
+
+ protected:
+  ClientHints client_hints_;
+};
+
+TEST_F(ClientHintsTest, HintsWellFormatted) {
+  UpdateScreenInfo(1.567f);
+  std::string hint = client_hints_.GetDevicePixelRatioHeader();
+  EXPECT_EQ("1.57", hint);
+}
+
+TEST_F(ClientHintsTest, HintsWellFormattedWithNonEnLocale) {
+  setlocale(LC_ALL, "fr_FR.UTF-8");
+  UpdateScreenInfo(1.567f);
+  std::string hint = client_hints_.GetDevicePixelRatioHeader();
+  EXPECT_EQ("1.57", hint);
+}
+
+TEST_F(ClientHintsTest, HintsHaveNonbogusValues) {
+  UpdateScreenInfo(-1.567f);
+  std::string hint = client_hints_.GetDevicePixelRatioHeader();
+  EXPECT_EQ("", hint);
+
+  UpdateScreenInfo(1.567f);
+  hint = client_hints_.GetDevicePixelRatioHeader();
+  EXPECT_EQ("1.57", hint);
+
+  UpdateScreenInfo(0.0f);
+  hint = client_hints_.GetDevicePixelRatioHeader();
+  // Hints should be last known good values.
+  EXPECT_EQ("1.57", hint);
+}
+
diff --git a/chrome/browser/profiles/profile_io_data.cc b/chrome/browser/profiles/profile_io_data.cc
index 8caf7f3..f45977a 100644
--- a/chrome/browser/profiles/profile_io_data.cc
+++ b/chrome/browser/profiles/profile_io_data.cc
@@ -772,6 +772,8 @@ void ProfileIOData::Init(content::ProtocolHandlerMap* protocol_handlers) const {
       new ChromeNetworkDelegate(
           io_thread_globals->extension_event_router_forwarder.get(),
           &enable_referrers_);
+  if (command_line.HasSwitch(switches::kEnableClientHints))
+    network_delegate->SetEnableClientHints();
   network_delegate->set_extension_info_map(
       profile_params_->extension_info_map.get());
   network_delegate->set_url_blacklist_manager(url_blacklist_manager_.get());
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index 2e7657f..050c8e2 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -1184,6 +1184,8 @@
         'browser/net/chrome_network_delegate.h',
         'browser/net/chrome_url_request_context.cc',
         'browser/net/chrome_url_request_context.h',
+        'browser/net/client_hints.cc',
+        'browser/net/client_hints.h',
         'browser/net/connect_interceptor.cc',
         'browser/net/connect_interceptor.h',
         'browser/net/connection_tester.cc',
diff --git a/chrome/chrome_tests_unit.gypi b/chrome/chrome_tests_unit.gypi
index cb16621..246134a 100644
--- a/chrome/chrome_tests_unit.gypi
+++ b/chrome/chrome_tests_unit.gypi
@@ -1001,6 +1001,7 @@
         'browser/net/chrome_fraudulent_certificate_reporter_unittest.cc',
         'browser/net/chrome_network_data_saving_metrics_unittest.cc',
         'browser/net/chrome_network_delegate_unittest.cc',
+        'browser/net/client_hints_unittest.cc',
         'browser/net/connection_tester_unittest.cc',
         'browser/net/dns_probe_runner_unittest.cc',
         'browser/net/dns_probe_service_unittest.cc',
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 2a6f133..15fb191 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -559,6 +559,9 @@ const char kEnableBatchedShutdown[]         = "enable-batched-shutdown";
 // Enables the benchmarking extensions.
 const char kEnableBenchmarking[]            = "enable-benchmarking";
 
+// Enables client hints, which adds hints about browser state to HTTP requests.
+const char kEnableClientHints[]             = "enable-client-hints";
+
 // Enables pushing cloud policy to Chrome using an invalidation service.
 const char kEnableCloudPolicyPush[]         = "enable-cloud-policy-push";
 
diff --git a/chrome/common/chrome_switches.h b/chrome/common/chrome_switches.h
index 8015e3d..58d7ffa 100644
--- a/chrome/common/chrome_switches.h
+++ b/chrome/common/chrome_switches.h
@@ -166,6 +166,7 @@ extern const char kEnableAuthNegotiatePort[];
 extern const char kEnableAutologin[];
 extern const char kEnableBatchedShutdown[];
 extern const char kEnableBenchmarking[];
+extern const char kEnableClientHints[];
 extern const char kEnableCloudPolicyPush[];
 extern const char kEnableCloudPrintProxy[];
 extern const char kEnableComponentCloudPolicy[];