[Chromedriver] Add Device Metrics override support to ChromeDriver via Capabilities

BUG=chromedriver:399

All of the code reviews for this patch were written against https://codereview.chromium.org/251933005/ . I used the wrong email address to create said patch, so I have created this one with the correct email address.

Review URL: https://codereview.chromium.org/288193004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271947 0039d316-1c4b-4281-b951-d872f2087c98

30 files changed, 762 insertions, 18 deletions

diff --git a/chrome/chrome_tests.gypi b/chrome/chrome_tests.gypi
index 94ea1e0..6dcc50b 100644
--- a/chrome/chrome_tests.gypi
+++ b/chrome/chrome_tests.gypi
@@ -402,6 +402,8 @@
         '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome/user_data_dir.h',
         '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome/embedded_automation_extension.cc',
         '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome/embedded_automation_extension.h',
+        '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome/mobile_device_list.cc',
+        '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome/mobile_device_list.h',
         'test/chromedriver/chrome/adb.h',
         'test/chromedriver/chrome/adb_impl.cc',
         'test/chromedriver/chrome/adb_impl.h',
@@ -425,6 +427,8 @@
         'test/chromedriver/chrome/debugger_tracker.h',
         'test/chromedriver/chrome/device_manager.cc',
         'test/chromedriver/chrome/device_manager.h',
+        'test/chromedriver/chrome/device_metrics.cc',
+        'test/chromedriver/chrome/device_metrics.h',
         'test/chromedriver/chrome/devtools_client.h',
         'test/chromedriver/chrome/devtools_client_impl.cc',
         'test/chromedriver/chrome/devtools_client_impl.h',
@@ -445,6 +449,10 @@
         'test/chromedriver/chrome/javascript_dialog_manager.h',
         'test/chromedriver/chrome/log.h',
         'test/chromedriver/chrome/log.cc',
+        'test/chromedriver/chrome/mobile_device.cc',
+        'test/chromedriver/chrome/mobile_device.h',
+        'test/chromedriver/chrome/mobile_emulation_override_manager.cc',
+        'test/chromedriver/chrome/mobile_emulation_override_manager.h',
         'test/chromedriver/chrome/navigation_tracker.cc',
         'test/chromedriver/chrome/navigation_tracker.h',
         'test/chromedriver/chrome/performance_logger.h',
@@ -550,6 +558,25 @@
           ],
           'message': 'Generating sources for embedding automation extension',
         },
+        {
+          'action_name': 'embed_mobile_devices_in_cpp',
+          'inputs': [
+            'test/chromedriver/cpp_source.py',
+            'test/chromedriver/embed_mobile_devices_in_cpp.py',
+            '../third_party/WebKit/Source/devtools/front_end/elements/OverridesView.js',
+          ],
+          'outputs': [
+            '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome/mobile_device_list.cc',
+            '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome/mobile_device_list.h',
+          ],
+          'action': [ 'python',
+                      'test/chromedriver/embed_mobile_devices_in_cpp.py',
+                      '--directory',
+                      '<(SHARED_INTERMEDIATE_DIR)/chrome/test/chromedriver/chrome',
+                      '../third_party/WebKit/Source/devtools/front_end/elements/OverridesView.js',
+          ],
+          'message': 'Generating sources for embedding mobile devices in chromedriver',
+        },
       ],
       # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
@@ -699,6 +726,7 @@
         'test/chromedriver/chrome/geolocation_override_manager_unittest.cc',
         'test/chromedriver/chrome/heap_snapshot_taker_unittest.cc',
         'test/chromedriver/chrome/javascript_dialog_manager_unittest.cc',
+        'test/chromedriver/chrome/mobile_emulation_override_manager_unittest.cc',
         'test/chromedriver/chrome/navigation_tracker_unittest.cc',
         'test/chromedriver/chrome/performance_logger_unittest.cc',
         'test/chromedriver/chrome/status_unittest.cc',
diff --git a/chrome/test/chromedriver/capabilities.cc b/chrome/test/chromedriver/capabilities.cc
index 518af52..b6fb0a5 100644
--- a/chrome/test/chromedriver/capabilities.cc
+++ b/chrome/test/chromedriver/capabilities.cc
@@ -17,6 +17,7 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
+#include "chrome/test/chromedriver/chrome/mobile_device.h"
 #include "chrome/test/chromedriver/chrome/status.h"
 #include "chrome/test/chromedriver/logging.h"
 #include "net/base/net_util.h"
@@ -84,6 +85,70 @@ Status ParseLogPath(const base::Value& option, Capabilities* capabilities) {
   return Status(kOk);
 }
 
+Status ParseDeviceName(std::string device_name, Capabilities* capabilities) {
+  scoped_ptr<MobileDevice> device;
+  Status status = FindMobileDevice(device_name, &device);
+
+  if (status.IsError()) {
+    return Status(kUnknownError,
+                  "'" + device_name + "' must be a valid device",
+                  status);
+  }
+
+  capabilities->device_metrics.reset(device->device_metrics.release());
+  capabilities->switches.SetSwitch("user-agent", device->user_agent);
+
+  return Status(kOk);
+}
+
+Status ParseMobileEmulation(const base::Value& option,
+                            Capabilities* capabilities) {
+  const base::DictionaryValue* mobile_emulation;
+  if (!option.GetAsDictionary(&mobile_emulation))
+    return Status(kUnknownError, "'mobileEmulation' must be a dictionary");
+
+  if (mobile_emulation->HasKey("deviceName")) {
+    // Cannot use any other options with deviceName.
+    if (mobile_emulation->size() > 1)
+      return Status(kUnknownError, "'deviceName' must be used alone");
+
+    std::string device_name;
+    if (!mobile_emulation->GetString("deviceName", &device_name))
+      return Status(kUnknownError, "'deviceName' must be a string");
+
+    return ParseDeviceName(device_name, capabilities);
+  }
+
+  if (mobile_emulation->HasKey("deviceMetrics")) {
+    const base::DictionaryValue* metrics;
+    if (!mobile_emulation->GetDictionary("deviceMetrics", &metrics))
+      return Status(kUnknownError, "'deviceMetrics' must be a dictionary");
+
+    int width;
+    int height;
+    double device_scale_factor;
+    if (!metrics->GetInteger("width", &width) ||
+        !metrics->GetInteger("height", &height) ||
+        !metrics->GetDouble("pixelRatio", &device_scale_factor))
+      return Status(kUnknownError, "invalid 'deviceMetrics'");
+
+    DeviceMetrics* device_metrics =
+        new DeviceMetrics(width, height, device_scale_factor);
+    capabilities->device_metrics =
+        scoped_ptr<DeviceMetrics>(device_metrics);
+  }
+
+  if (mobile_emulation->HasKey("userAgent")) {
+    std::string user_agent;
+    if (!mobile_emulation->GetString("userAgent", &user_agent))
+      return Status(kUnknownError, "'userAgent' must be a string");
+
+    capabilities->switches.SetSwitch("user-agent", user_agent);
+  }
+
+  return Status(kOk);
+}
+
 Status ParseSwitches(const base::Value& option,
                      Capabilities* capabilities) {
   const base::ListValue* switches_list = NULL;
@@ -272,6 +337,7 @@ Status ParseChromeOptions(
     parser_map["args"] = base::Bind(&ParseSwitches);
     parser_map["binary"] = base::Bind(&ParseFilePath, &capabilities->binary);
     parser_map["detach"] = base::Bind(&ParseBoolean, &capabilities->detach);
+    parser_map["mobileEmulation"] = base::Bind(&ParseMobileEmulation);
     parser_map["excludeSwitches"] = base::Bind(&ParseExcludeSwitches);
     parser_map["extensions"] = base::Bind(&ParseExtensions);
     parser_map["forceDevToolsScreenshot"] = base::Bind(
diff --git a/chrome/test/chromedriver/capabilities.h b/chrome/test/chromedriver/capabilities.h
index 998c56a..c21c045 100644
--- a/chrome/test/chromedriver/capabilities.h
+++ b/chrome/test/chromedriver/capabilities.h
@@ -14,6 +14,7 @@
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
+#include "chrome/test/chromedriver/chrome/device_metrics.h"
 #include "chrome/test/chromedriver/chrome/log.h"
 #include "chrome/test/chromedriver/net/net_util.h"
 
@@ -91,6 +92,9 @@ struct Capabilities {
   // ChromeDriver dies.
   bool detach;
 
+  // Device metrics for use in Device Emulation.
+  scoped_ptr<DeviceMetrics> device_metrics;
+
   // Set of switches which should be removed from default list when launching
   // Chrome.
   std::set<std::string> exclude_switches;
diff --git a/chrome/test/chromedriver/capabilities_unittest.cc b/chrome/test/chromedriver/capabilities_unittest.cc
index f4b313e..ea1e87c 100644
--- a/chrome/test/chromedriver/capabilities_unittest.cc
+++ b/chrome/test/chromedriver/capabilities_unittest.cc
@@ -361,3 +361,98 @@ TEST(ParseCapabilities, UseExistingBrowser) {
   ASSERT_EQ("abc", capabilities.debugger_address.host());
   ASSERT_EQ(123, capabilities.debugger_address.port());
 }
+
+TEST(ParseCapabilities, MobileEmulationUserAgent) {
+  Capabilities capabilities;
+  base::DictionaryValue mobile_emulation;
+  mobile_emulation.SetString("userAgent", "Agent Smith");
+  base::DictionaryValue caps;
+  caps.Set("chromeOptions.mobileEmulation", mobile_emulation.DeepCopy());
+  Status status = capabilities.Parse(caps);
+  ASSERT_TRUE(status.IsOk());
+
+  ASSERT_EQ(1u, capabilities.switches.GetSize());
+  ASSERT_TRUE(capabilities.switches.HasSwitch("user-agent"));
+  ASSERT_EQ("Agent Smith", capabilities.switches.GetSwitchValue("user-agent"));
+}
+
+TEST(ParseCapabilities, MobileEmulationDeviceMetrics) {
+  Capabilities capabilities;
+  base::DictionaryValue mobile_emulation;
+  mobile_emulation.SetInteger("deviceMetrics.width", 360);
+  mobile_emulation.SetInteger("deviceMetrics.height", 640);
+  mobile_emulation.SetDouble("deviceMetrics.pixelRatio", 3.0);
+  base::DictionaryValue caps;
+  caps.Set("chromeOptions.mobileEmulation", mobile_emulation.DeepCopy());
+  Status status = capabilities.Parse(caps);
+  ASSERT_TRUE(status.IsOk());
+
+  ASSERT_EQ(360, capabilities.device_metrics->width);
+  ASSERT_EQ(640, capabilities.device_metrics->height);
+  ASSERT_EQ(3.0, capabilities.device_metrics->device_scale_factor);
+}
+
+TEST(ParseCapabilities, MobileEmulationDeviceName) {
+  Capabilities capabilities;
+  base::DictionaryValue mobile_emulation;
+  mobile_emulation.SetString("deviceName", "Google Nexus 5");
+  base::DictionaryValue caps;
+  caps.Set("chromeOptions.mobileEmulation", mobile_emulation.DeepCopy());
+  Status status = capabilities.Parse(caps);
+  ASSERT_TRUE(status.IsOk());
+
+  ASSERT_EQ(1u, capabilities.switches.GetSize());
+  ASSERT_TRUE(capabilities.switches.HasSwitch("user-agent"));
+  ASSERT_EQ(
+      "Mozilla/5.0 (Linux; Android 4.2.1; en-us; Nexus 5 Build/JOP40D) "
+      "AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.166 "
+      "Mobile Safari/535.19",
+      capabilities.switches.GetSwitchValue("user-agent"));
+
+  ASSERT_EQ(360, capabilities.device_metrics->width);
+  ASSERT_EQ(640, capabilities.device_metrics->height);
+  ASSERT_EQ(3.0, capabilities.device_metrics->device_scale_factor);
+}
+
+TEST(ParseCapabilities, MobileEmulationNotDict) {
+  Capabilities capabilities;
+  base::DictionaryValue caps;
+  caps.SetString("chromeOptions.mobileEmulation", "Google Nexus 5");
+  Status status = capabilities.Parse(caps);
+  ASSERT_FALSE(status.IsOk());
+}
+
+TEST(ParseCapabilities, MobileEmulationDeviceMetricsNotDict) {
+  Capabilities capabilities;
+  base::DictionaryValue mobile_emulation;
+  mobile_emulation.SetInteger("deviceMetrics", 360);
+  base::DictionaryValue caps;
+  caps.Set("chromeOptions.mobileEmulation", mobile_emulation.DeepCopy());
+  Status status = capabilities.Parse(caps);
+  ASSERT_FALSE(status.IsOk());
+}
+
+TEST(ParseCapabilities, MobileEmulationDeviceMetricsNotNumbers) {
+  Capabilities capabilities;
+  base::DictionaryValue mobile_emulation;
+  mobile_emulation.SetString("deviceMetrics.width", "360");
+  mobile_emulation.SetString("deviceMetrics.height", "640");
+  mobile_emulation.SetString("deviceMetrics.pixelRatio", "3.0");
+  base::DictionaryValue caps;
+  caps.Set("chromeOptions.mobileEmulation", mobile_emulation.DeepCopy());
+  Status status = capabilities.Parse(caps);
+  ASSERT_FALSE(status.IsOk());
+}
+
+TEST(ParseCapabilities, MobileEmulationBadDict) {
+  Capabilities capabilities;
+  base::DictionaryValue mobile_emulation;
+  mobile_emulation.SetString("deviceName", "Google Nexus 5");
+  mobile_emulation.SetInteger("deviceMetrics.width", 360);
+  mobile_emulation.SetInteger("deviceMetrics.height", 640);
+  mobile_emulation.SetDouble("deviceMetrics.pixelRatio", 3.0);
+  base::DictionaryValue caps;
+  caps.Set("chromeOptions.mobileEmulation", mobile_emulation.DeepCopy());
+  Status status = capabilities.Parse(caps);
+  ASSERT_FALSE(status.IsOk());
+}
diff --git a/chrome/test/chromedriver/chrome/chrome.h b/chrome/test/chromedriver/chrome/chrome.h
index 56885bc..277c58d 100644
--- a/chrome/test/chromedriver/chrome/chrome.h
+++ b/chrome/test/chromedriver/chrome/chrome.h
@@ -40,6 +40,9 @@ class Chrome {
   // Get the operation system where Chrome is running.
   virtual std::string GetOperatingSystemName() = 0;
 
+  // Return whether the mobileEmulation capability has been enabled.
+  virtual bool IsMobileEmulationEnabled() const = 0;
+
   // Quits Chrome.
   virtual Status Quit() = 0;
 };
diff --git a/chrome/test/chromedriver/chrome/chrome_desktop_impl.cc b/chrome/test/chromedriver/chrome/chrome_desktop_impl.cc
index 8cdd130..d737249 100644
--- a/chrome/test/chromedriver/chrome/chrome_desktop_impl.cc
+++ b/chrome/test/chromedriver/chrome/chrome_desktop_impl.cc
@@ -117,7 +117,8 @@ Status ChromeDesktopImpl::WaitForPageToLoad(const std::string& url,
   scoped_ptr<WebView> web_view_tmp(
       new WebViewImpl(id,
                       devtools_http_client_->browser_info(),
-                      devtools_http_client_->CreateClient(id)));
+                      devtools_http_client_->CreateClient(id),
+                      devtools_http_client_->device_metrics()));
   Status status = web_view_tmp->ConnectIfNecessary();
   if (status.IsError())
     return status;
@@ -155,6 +156,10 @@ std::string ChromeDesktopImpl::GetOperatingSystemName() {
   return base::SysInfo::OperatingSystemName();
 }
 
+bool ChromeDesktopImpl::IsMobileEmulationEnabled() const {
+  return devtools_http_client_->device_metrics() != NULL;
+}
+
 Status ChromeDesktopImpl::QuitImpl() {
   if (!KillProcess(process_))
     return Status(kUnknownError, "cannot kill Chrome");
diff --git a/chrome/test/chromedriver/chrome/chrome_desktop_impl.h b/chrome/test/chromedriver/chrome/chrome_desktop_impl.h
index c8e86a7..d448419 100644
--- a/chrome/test/chromedriver/chrome/chrome_desktop_impl.h
+++ b/chrome/test/chromedriver/chrome/chrome_desktop_impl.h
@@ -49,6 +49,7 @@ class ChromeDesktopImpl : public ChromeImpl {
   virtual std::string GetOperatingSystemName() OVERRIDE;
 
   // Overridden from ChromeImpl:
+  virtual bool IsMobileEmulationEnabled() const OVERRIDE;
   virtual Status QuitImpl() OVERRIDE;
 
   const base::CommandLine& command() const;
diff --git a/chrome/test/chromedriver/chrome/chrome_impl.cc b/chrome/test/chromedriver/chrome/chrome_impl.cc
index f0b87d6..7f796d2 100644
--- a/chrome/test/chromedriver/chrome/chrome_impl.cc
+++ b/chrome/test/chromedriver/chrome/chrome_impl.cc
@@ -83,7 +83,10 @@ Status ChromeImpl::GetWebViewIds(std::list<std::string>* web_view_ids) {
         // OnConnected will fire when DevToolsClient connects later.
       }
       web_views_.push_back(make_linked_ptr(new WebViewImpl(
-          view.id, devtools_http_client_->browser_info(), client.Pass())));
+          view.id,
+          devtools_http_client_->browser_info(),
+          client.Pass(),
+          devtools_http_client_->device_metrics())));
     }
   }
 
@@ -125,6 +128,10 @@ Status ChromeImpl::ActivateWebView(const std::string& id) {
   return devtools_http_client_->ActivateWebView(id);
 }
 
+bool ChromeImpl::IsMobileEmulationEnabled() const {
+  return false;
+}
+
 Status ChromeImpl::Quit() {
   Status status = QuitImpl();
   if (status.IsOk())
diff --git a/chrome/test/chromedriver/chrome/chrome_impl.h b/chrome/test/chromedriver/chrome/chrome_impl.h
index 01ad596..d852351 100644
--- a/chrome/test/chromedriver/chrome/chrome_impl.h
+++ b/chrome/test/chromedriver/chrome/chrome_impl.h
@@ -37,6 +37,7 @@ class ChromeImpl : public Chrome {
                                 WebView** web_view) OVERRIDE;
   virtual Status CloseWebView(const std::string& id) OVERRIDE;
   virtual Status ActivateWebView(const std::string& id) OVERRIDE;
+  virtual bool IsMobileEmulationEnabled() const OVERRIDE;
   virtual Status Quit() OVERRIDE;
 
  protected:
diff --git a/chrome/test/chromedriver/chrome/device_metrics.cc b/chrome/test/chromedriver/chrome/device_metrics.cc
new file mode 100644
index 0000000..059e55d
--- /dev/null
+++ b/chrome/test/chromedriver/chrome/device_metrics.cc
@@ -0,0 +1,16 @@
+// Copyright 2014 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/test/chromedriver/chrome/device_metrics.h"
+
+DeviceMetrics::DeviceMetrics(int width, int height, double device_scale_factor)
+  : width(width),
+    height(height),
+    device_scale_factor(device_scale_factor),
+    emulate_viewport(false),
+    fit_window(true),
+    text_autosizing(true),
+    font_scale_factor(1) {}
+
+DeviceMetrics::~DeviceMetrics() {}
diff --git a/chrome/test/chromedriver/chrome/device_metrics.h b/chrome/test/chromedriver/chrome/device_metrics.h
new file mode 100644
index 0000000..d40159b
--- /dev/null
+++ b/chrome/test/chromedriver/chrome/device_metrics.h
@@ -0,0 +1,21 @@
+// Copyright 2014 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_TEST_CHROMEDRIVER_CHROME_DEVICE_METRICS_H_
+#define CHROME_TEST_CHROMEDRIVER_CHROME_DEVICE_METRICS_H_
+
+struct DeviceMetrics {
+  DeviceMetrics(int width, int height, double device_scale_factor);
+  ~DeviceMetrics();
+
+  int width;
+  int height;
+  double device_scale_factor;
+  bool emulate_viewport;
+  bool fit_window;
+  bool text_autosizing;
+  double font_scale_factor;
+};
+
+#endif  // CHROME_TEST_CHROMEDRIVER_CHROME_DEVICE_METRICS_H_
diff --git a/chrome/test/chromedriver/chrome/devtools_http_client.cc b/chrome/test/chromedriver/chrome/devtools_http_client.cc
index 2d380a8..99ff945 100644
--- a/chrome/test/chromedriver/chrome/devtools_http_client.cc
+++ b/chrome/test/chromedriver/chrome/devtools_http_client.cc
@@ -13,6 +13,7 @@
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 #include "base/values.h"
+#include "chrome/test/chromedriver/chrome/device_metrics.h"
 #include "chrome/test/chromedriver/chrome/devtools_client_impl.h"
 #include "chrome/test/chromedriver/chrome/log.h"
 #include "chrome/test/chromedriver/chrome/status.h"
@@ -67,12 +68,14 @@ const WebViewInfo* WebViewsInfo::GetForId(const std::string& id) const {
 DevToolsHttpClient::DevToolsHttpClient(
     const NetAddress& address,
     scoped_refptr<URLRequestContextGetter> context_getter,
-    const SyncWebSocketFactory& socket_factory)
+    const SyncWebSocketFactory& socket_factory,
+    scoped_ptr<DeviceMetrics> device_metrics)
     : context_getter_(context_getter),
       socket_factory_(socket_factory),
       server_url_("http://" + address.ToString()),
       web_socket_url_prefix_(base::StringPrintf(
-          "ws://%s/devtools/page/", address.ToString().c_str())) {}
+          "ws://%s/devtools/page/", address.ToString().c_str())),
+      device_metrics_(device_metrics.Pass()) {}
 
 DevToolsHttpClient::~DevToolsHttpClient() {}
 
@@ -196,6 +199,10 @@ const BrowserInfo* DevToolsHttpClient::browser_info() {
   return &browser_info_;
 }
 
+const DeviceMetrics* DevToolsHttpClient::device_metrics() {
+  return device_metrics_.get();
+}
+
 Status DevToolsHttpClient::GetVersion(std::string* browser_version,
                                       std::string* blink_version) {
   std::string data;
@@ -248,7 +255,7 @@ Status DevToolsHttpClient::CloseFrontends(const std::string& for_client_id) {
         *it,
         base::Bind(&FakeCloseFrontends)));
     scoped_ptr<WebViewImpl> web_view(
-        new WebViewImpl(*it, &browser_info_, client.Pass()));
+        new WebViewImpl(*it, &browser_info_, client.Pass(), NULL));
 
     status = web_view->ConnectIfNecessary();
     // Ignore disconnected error, because the debugger might have closed when
diff --git a/chrome/test/chromedriver/chrome/devtools_http_client.h b/chrome/test/chromedriver/chrome/devtools_http_client.h
index 693f0c0..1e1c5eb 100644
--- a/chrome/test/chromedriver/chrome/devtools_http_client.h
+++ b/chrome/test/chromedriver/chrome/devtools_http_client.h
@@ -17,6 +17,7 @@ namespace base {
 class TimeDelta;
 }
 
+struct DeviceMetrics;
 class DevToolsClient;
 class NetAddress;
 class Status;
@@ -64,7 +65,8 @@ class DevToolsHttpClient {
   DevToolsHttpClient(
       const NetAddress& address,
       scoped_refptr<URLRequestContextGetter> context_getter,
-      const SyncWebSocketFactory& socket_factory);
+      const SyncWebSocketFactory& socket_factory,
+      scoped_ptr<DeviceMetrics> device_metrics);
   ~DevToolsHttpClient();
 
   Status Init(const base::TimeDelta& timeout);
@@ -78,6 +80,7 @@ class DevToolsHttpClient {
   Status ActivateWebView(const std::string& id);
 
   const BrowserInfo* browser_info();
+  const DeviceMetrics* device_metrics();
 
  private:
   Status GetVersion(std::string* browser_version, std::string* blink_version);
@@ -91,6 +94,7 @@ class DevToolsHttpClient {
   std::string server_url_;
   std::string web_socket_url_prefix_;
   BrowserInfo browser_info_;
+  scoped_ptr<DeviceMetrics> device_metrics_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsHttpClient);
 };
diff --git a/chrome/test/chromedriver/chrome/mobile_device.cc b/chrome/test/chromedriver/chrome/mobile_device.cc
new file mode 100644
index 0000000..fe6b4d1
--- /dev/null
+++ b/chrome/test/chromedriver/chrome/mobile_device.cc
@@ -0,0 +1,87 @@
+// Copyright 2014 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/json/json_reader.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/values.h"
+#include "chrome/test/chromedriver/chrome/mobile_device.h"
+#include "chrome/test/chromedriver/chrome/mobile_device_list.h"
+#include "chrome/test/chromedriver/chrome/status.h"
+
+MobileDevice::MobileDevice() {}
+MobileDevice::~MobileDevice() {}
+
+Status FindMobileDevice(std::string device_name,
+                        scoped_ptr<MobileDevice>* mobile_device) {
+  base::JSONReader json_reader(base::JSON_ALLOW_TRAILING_COMMAS);
+  scoped_ptr<base::Value> devices_value;
+  devices_value.reset(json_reader.ReadToValue(kMobileDevices));
+  if (!devices_value.get())
+    return Status(kUnknownError,
+                  "could not parse mobile device list because " +
+                  json_reader.GetErrorMessage());
+
+  base::ListValue* mobile_devices;
+  if (!devices_value->GetAsList(&mobile_devices))
+    return Status(kUnknownError, "malformed device metrics list");
+
+  for (base::ListValue::iterator it = mobile_devices->begin();
+       it != mobile_devices->end();
+       ++it) {
+    base::ListValue* device = NULL;
+    if (!(*it)->GetAsList(&device)) {
+      return Status(kUnknownError,
+                    "malformed device in list: should be an array");
+    }
+
+    if (device != NULL) {
+      std::string name;
+      if (!device->GetString(0, &name)) {
+        return Status(kUnknownError,
+                      "malformed device name: should be a string");
+      }
+      if (name != device_name)
+        continue;
+
+      scoped_ptr<MobileDevice> tmp_mobile_device(new MobileDevice());
+      std::string device_metrics_string;
+      if (!device->GetString(1, &tmp_mobile_device->user_agent)) {
+        return Status(kUnknownError,
+                      "malformed device user agent: should be a string");
+      }
+      if (!device->GetString(2, &device_metrics_string)) {
+        return Status(kUnknownError,
+                      "malformed device metrics: should be a string");
+      }
+      std::vector<std::string> metrics_vector;
+      base::SplitString(device_metrics_string, 'x', &metrics_vector);
+      if (metrics_vector.size() < 3)
+        return Status(kUnknownError, "malformed device metrics string");
+
+      int width = 0;
+      int height = 0;
+      double device_scale_factor = 0.0;
+      if (!base::StringToInt(metrics_vector[0], &width)) {
+        return Status(kUnknownError,
+                      "malformed device width: should be an integer");
+      }
+      if (!base::StringToInt(metrics_vector[1], &height)) {
+        return Status(kUnknownError,
+                      "malformed device height: should be an integer");
+      }
+      if (!base::StringToDouble(metrics_vector[2], &device_scale_factor)) {
+        return Status(kUnknownError,
+                      "malformed device scale factor: should be a double");
+      }
+      tmp_mobile_device->device_metrics.reset(
+          new DeviceMetrics(width, height, device_scale_factor));
+
+      *mobile_device = tmp_mobile_device.Pass();
+      return Status(kOk);
+    }
+  }
+
+  return Status(kUnknownError, "must be a valid device");
+}
diff --git a/chrome/test/chromedriver/chrome/mobile_device.h b/chrome/test/chromedriver/chrome/mobile_device.h
new file mode 100644
index 0000000..fbb91eb
--- /dev/null
+++ b/chrome/test/chromedriver/chrome/mobile_device.h
@@ -0,0 +1,24 @@
+// Copyright 2014 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_TEST_CHROMEDRIVER_CHROME_MOBILE_DEVICE_H_
+#define CHROME_TEST_CHROMEDRIVER_CHROME_MOBILE_DEVICE_H_
+
+#include <string>
+#include "base/memory/scoped_ptr.h"
+#include "chrome/test/chromedriver/chrome/device_metrics.h"
+
+class Status;
+
+struct MobileDevice {
+  MobileDevice();
+  ~MobileDevice();
+  scoped_ptr<DeviceMetrics> device_metrics;
+  std::string user_agent;
+};
+
+Status FindMobileDevice(std::string device_name,
+                        scoped_ptr<MobileDevice>* mobile_device);
+
+#endif  // CHROME_TEST_CHROMEDRIVER_CHROME_MOBILE_DEVICE_H_
diff --git a/chrome/test/chromedriver/chrome/mobile_emulation_override_manager.cc b/chrome/test/chromedriver/chrome/mobile_emulation_override_manager.cc
new file mode 100644
index 0000000..4a69c66
--- /dev/null
+++ b/chrome/test/chromedriver/chrome/mobile_emulation_override_manager.cc
@@ -0,0 +1,55 @@
+// Copyright 2014 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/values.h"
+#include "chrome/test/chromedriver/chrome/device_metrics.h"
+#include "chrome/test/chromedriver/chrome/devtools_client.h"
+#include "chrome/test/chromedriver/chrome/mobile_emulation_override_manager.h"
+#include "chrome/test/chromedriver/chrome/status.h"
+
+MobileEmulationOverrideManager::MobileEmulationOverrideManager(
+    DevToolsClient* client,
+    const DeviceMetrics* device_metrics)
+    : client_(client), overridden_device_metrics_(device_metrics) {
+  if (overridden_device_metrics_)
+    client_->AddListener(this);
+}
+
+MobileEmulationOverrideManager::~MobileEmulationOverrideManager() {
+}
+
+Status MobileEmulationOverrideManager::OnConnected(DevToolsClient* client) {
+  return ApplyOverrideIfNeeded();
+}
+
+Status MobileEmulationOverrideManager::OnEvent(
+    DevToolsClient* client,
+    const std::string& method,
+    const base::DictionaryValue& params) {
+  if (method == "Page.frameNavigated") {
+    const base::Value* unused_value;
+    if (!params.Get("frame.parentId", &unused_value))
+      return ApplyOverrideIfNeeded();
+  }
+  return Status(kOk);
+}
+
+Status MobileEmulationOverrideManager::ApplyOverrideIfNeeded() {
+  if (overridden_device_metrics_ == NULL)
+    return Status(kOk);
+
+  base::DictionaryValue params;
+  params.SetInteger("width", overridden_device_metrics_->width);
+  params.SetInteger("height", overridden_device_metrics_->height);
+  params.SetDouble("deviceScaleFactor",
+                   overridden_device_metrics_->device_scale_factor);
+  params.SetBoolean("emulateViewport",
+                    overridden_device_metrics_->emulate_viewport);
+  params.SetBoolean("fitWindow", overridden_device_metrics_->fit_window);
+  params.SetBoolean("textAutosizing",
+                    overridden_device_metrics_->text_autosizing);
+  params.SetDouble("fontScaleFactor",
+                   overridden_device_metrics_->font_scale_factor);
+  return client_->SendCommand("Page.setDeviceMetricsOverride", params);
+}
diff --git a/chrome/test/chromedriver/chrome/mobile_emulation_override_manager.h b/chrome/test/chromedriver/chrome/mobile_emulation_override_manager.h
new file mode 100644
index 0000000..4c08f44
--- /dev/null
+++ b/chrome/test/chromedriver/chrome/mobile_emulation_override_manager.h
@@ -0,0 +1,46 @@
+// Copyright 2014 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_TEST_CHROMEDRIVER_CHROME_MOBILE_EMULATION_OVERRIDE_MANAGER_H_
+#define CHROME_TEST_CHROMEDRIVER_CHROME_MOBILE_EMULATION_OVERRIDE_MANAGER_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/test/chromedriver/chrome/devtools_event_listener.h"
+
+namespace base {
+class DictionaryValue;
+}
+
+class DevToolsClient;
+struct DeviceMetrics;
+class Status;
+
+// Overrides the device metrics, if requested, for the duration of the
+// given |DevToolsClient|'s lifetime.
+class MobileEmulationOverrideManager : public DevToolsEventListener {
+ public:
+  MobileEmulationOverrideManager(DevToolsClient* client,
+                                 const DeviceMetrics* device_metrics);
+  virtual ~MobileEmulationOverrideManager();
+
+  // Overridden from DevToolsEventListener:
+  virtual Status OnConnected(DevToolsClient* client) OVERRIDE;
+  virtual Status OnEvent(DevToolsClient* client,
+                         const std::string& method,
+                         const base::DictionaryValue& params) OVERRIDE;
+
+ private:
+  Status ApplyOverrideIfNeeded();
+
+  DevToolsClient* client_;
+  const DeviceMetrics* overridden_device_metrics_;
+
+  DISALLOW_COPY_AND_ASSIGN(MobileEmulationOverrideManager);
+};
+
+#endif  // CHROME_TEST_CHROMEDRIVER_CHROME_MOBILE_EMULATION_OVERRIDE_MANAGER_H_
diff --git a/chrome/test/chromedriver/chrome/mobile_emulation_override_manager_unittest.cc b/chrome/test/chromedriver/chrome/mobile_emulation_override_manager_unittest.cc
new file mode 100644
index 0000000..a318783
--- /dev/null
+++ b/chrome/test/chromedriver/chrome/mobile_emulation_override_manager_unittest.cc
@@ -0,0 +1,117 @@
+// Copyright 2014 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 <string>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/values.h"
+#include "chrome/test/chromedriver/chrome/device_metrics.h"
+#include "chrome/test/chromedriver/chrome/mobile_emulation_override_manager.h"
+#include "chrome/test/chromedriver/chrome/status.h"
+#include "chrome/test/chromedriver/chrome/stub_devtools_client.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+struct Command {
+  Command() {}
+  Command(const std::string& method, const base::DictionaryValue& params)
+      : method(method) {
+    this->params.MergeDictionary(&params);
+  }
+  Command(const Command& command) {
+    *this = command;
+  }
+  Command& operator=(const Command& command) {
+    method = command.method;
+    params.Clear();
+    params.MergeDictionary(&command.params);
+    return *this;
+  }
+  ~Command() {}
+
+  std::string method;
+  base::DictionaryValue params;
+};
+
+class RecorderDevToolsClient : public StubDevToolsClient {
+ public:
+  RecorderDevToolsClient() {}
+  virtual ~RecorderDevToolsClient() {}
+
+  // Overridden from StubDevToolsClient:
+  virtual Status SendCommandAndGetResult(
+      const std::string& method,
+      const base::DictionaryValue& params,
+      scoped_ptr<base::DictionaryValue>* result) OVERRIDE {
+    commands_.push_back(Command(method, params));
+    return Status(kOk);
+  }
+
+  std::vector<Command> commands_;
+};
+
+void AssertDeviceMetricsCommand(const Command& command,
+                              const DeviceMetrics& device_metrics) {
+  ASSERT_EQ("Page.setDeviceMetricsOverride", command.method);
+  int width, height;
+  double device_scale_factor, font_scale_factor;
+  bool emulate_viewport, fit_window, text_autosizing;
+  ASSERT_TRUE(command.params.GetInteger("width", &width));
+  ASSERT_TRUE(command.params.GetInteger("height", &height));
+  ASSERT_TRUE(command.params.GetDouble("deviceScaleFactor",
+                                       &device_scale_factor));
+  ASSERT_TRUE(command.params.GetBoolean("emulateViewport", &emulate_viewport));
+  ASSERT_TRUE(command.params.GetBoolean("fitWindow", &fit_window));
+  ASSERT_TRUE(command.params.GetBoolean("textAutosizing", &text_autosizing));
+  ASSERT_TRUE(command.params.GetDouble("fontScaleFactor", &font_scale_factor));
+  ASSERT_EQ(device_metrics.width, width);
+  ASSERT_EQ(device_metrics.height, height);
+  ASSERT_EQ(device_metrics.device_scale_factor, device_scale_factor);
+  ASSERT_EQ(device_metrics.emulate_viewport, emulate_viewport);
+  ASSERT_EQ(device_metrics.fit_window, fit_window);
+  ASSERT_EQ(device_metrics.text_autosizing, text_autosizing);
+  ASSERT_EQ(device_metrics.font_scale_factor, font_scale_factor);
+}
+
+}  // namespace
+
+TEST(MobileEmulationOverrideManager, SendsCommandOnConnect) {
+  RecorderDevToolsClient client;
+  DeviceMetrics device_metrics(1, 2, 3.0);
+  MobileEmulationOverrideManager manager(&client, &device_metrics);
+  ASSERT_EQ(0u, client.commands_.size());
+  ASSERT_EQ(kOk, manager.OnConnected(&client).code());
+
+  ASSERT_EQ(1u, client.commands_.size());
+  ASSERT_EQ(kOk, manager.OnConnected(&client).code());
+  ASSERT_EQ(2u, client.commands_.size());
+  ASSERT_NO_FATAL_FAILURE(
+      AssertDeviceMetricsCommand(client.commands_[1], device_metrics));
+}
+
+TEST(MobileEmulationOverrideManager, SendsCommandOnNavigation) {
+  RecorderDevToolsClient client;
+  DeviceMetrics device_metrics(1, 2, 3.0);
+  MobileEmulationOverrideManager manager(&client, &device_metrics);
+  base::DictionaryValue main_frame_params;
+  ASSERT_EQ(kOk,
+            manager.OnEvent(&client, "Page.frameNavigated", main_frame_params)
+                .code());
+  ASSERT_EQ(1u, client.commands_.size());
+  ASSERT_EQ(kOk,
+            manager.OnEvent(&client, "Page.frameNavigated", main_frame_params)
+                .code());
+  ASSERT_EQ(2u, client.commands_.size());
+  ASSERT_NO_FATAL_FAILURE(
+      AssertDeviceMetricsCommand(client.commands_[1], device_metrics));
+
+  base::DictionaryValue sub_frame_params;
+  sub_frame_params.SetString("frame.parentId", "id");
+  ASSERT_EQ(
+      kOk,
+      manager.OnEvent(&client, "Page.frameNavigated", sub_frame_params).code());
+  ASSERT_EQ(2u, client.commands_.size());
+}
diff --git a/chrome/test/chromedriver/chrome/stub_chrome.cc b/chrome/test/chromedriver/chrome/stub_chrome.cc
index 5e1cbe1..394a183 100644
--- a/chrome/test/chromedriver/chrome/stub_chrome.cc
+++ b/chrome/test/chromedriver/chrome/stub_chrome.cc
@@ -43,6 +43,10 @@ std::string StubChrome::GetOperatingSystemName() {
   return std::string();
 }
 
+bool StubChrome::IsMobileEmulationEnabled() const {
+  return false;
+}
+
 Status StubChrome::Quit() {
   return Status(kOk);
 }
diff --git a/chrome/test/chromedriver/chrome/stub_chrome.h b/chrome/test/chromedriver/chrome/stub_chrome.h
index 1e07aa0..ba09328 100644
--- a/chrome/test/chromedriver/chrome/stub_chrome.h
+++ b/chrome/test/chromedriver/chrome/stub_chrome.h
@@ -30,6 +30,7 @@ class StubChrome : public Chrome {
   virtual Status CloseWebView(const std::string& id) OVERRIDE;
   virtual Status ActivateWebView(const std::string& id) OVERRIDE;
   virtual std::string GetOperatingSystemName() OVERRIDE;
+  virtual bool IsMobileEmulationEnabled() const OVERRIDE;
   virtual Status Quit() OVERRIDE;
 
  private:
diff --git a/chrome/test/chromedriver/chrome/web_view_impl.cc b/chrome/test/chromedriver/chrome/web_view_impl.cc
index 4403e89..f49485d 100644
--- a/chrome/test/chromedriver/chrome/web_view_impl.cc
+++ b/chrome/test/chromedriver/chrome/web_view_impl.cc
@@ -21,6 +21,7 @@
 #include "chrome/test/chromedriver/chrome/heap_snapshot_taker.h"
 #include "chrome/test/chromedriver/chrome/javascript_dialog_manager.h"
 #include "chrome/test/chromedriver/chrome/js.h"
+#include "chrome/test/chromedriver/chrome/mobile_emulation_override_manager.h"
 #include "chrome/test/chromedriver/chrome/navigation_tracker.h"
 #include "chrome/test/chromedriver/chrome/status.h"
 #include "chrome/test/chromedriver/chrome/ui_events.h"
@@ -114,13 +115,16 @@ const char* GetAsString(KeyEventType type) {
 
 WebViewImpl::WebViewImpl(const std::string& id,
                          const BrowserInfo* browser_info,
-                         scoped_ptr<DevToolsClient> client)
+                         scoped_ptr<DevToolsClient> client,
+                         const DeviceMetrics* device_metrics)
     : id_(id),
       browser_info_(browser_info),
       dom_tracker_(new DomTracker(client.get())),
       frame_tracker_(new FrameTracker(client.get())),
       navigation_tracker_(new NavigationTracker(client.get(), browser_info)),
       dialog_manager_(new JavaScriptDialogManager(client.get())),
+      mobile_emulation_override_manager_(
+          new MobileEmulationOverrideManager(client.get(), device_metrics)),
       geolocation_override_manager_(
           new GeolocationOverrideManager(client.get())),
       heap_snapshot_taker_(new HeapSnapshotTaker(client.get())),
diff --git a/chrome/test/chromedriver/chrome/web_view_impl.h b/chrome/test/chromedriver/chrome/web_view_impl.h
index c1424c8..06718b7 100644
--- a/chrome/test/chromedriver/chrome/web_view_impl.h
+++ b/chrome/test/chromedriver/chrome/web_view_impl.h
@@ -21,10 +21,12 @@ class Value;
 
 struct BrowserInfo;
 class DebuggerTracker;
+struct DeviceMetrics;
 class DevToolsClient;
 class DomTracker;
 class FrameTracker;
 class GeolocationOverrideManager;
+class MobileEmulationOverrideManager;
 class HeapSnapshotTaker;
 struct KeyEvent;
 struct MouseEvent;
@@ -36,6 +38,10 @@ class WebViewImpl : public WebView {
   WebViewImpl(const std::string& id,
               const BrowserInfo* browser_info,
               scoped_ptr<DevToolsClient> client);
+  WebViewImpl(const std::string& id,
+              const BrowserInfo* browser_info,
+              scoped_ptr<DevToolsClient> client,
+              const DeviceMetrics* device_metrics);
   virtual ~WebViewImpl();
 
   // Overridden from WebView:
@@ -111,6 +117,7 @@ class WebViewImpl : public WebView {
   scoped_ptr<FrameTracker> frame_tracker_;
   scoped_ptr<NavigationTracker> navigation_tracker_;
   scoped_ptr<JavaScriptDialogManager> dialog_manager_;
+  scoped_ptr<MobileEmulationOverrideManager> mobile_emulation_override_manager_;
   scoped_ptr<GeolocationOverrideManager> geolocation_override_manager_;
   scoped_ptr<HeapSnapshotTaker> heap_snapshot_taker_;
   scoped_ptr<DebuggerTracker> debugger_;
diff --git a/chrome/test/chromedriver/chrome_launcher.cc b/chrome/test/chromedriver/chrome_launcher.cc
index 24037f5..49d5f05 100644
--- a/chrome/test/chromedriver/chrome_launcher.cc
+++ b/chrome/test/chromedriver/chrome_launcher.cc
@@ -157,9 +157,14 @@ Status WaitForDevToolsAndCheckVersion(
     const NetAddress& address,
     URLRequestContextGetter* context_getter,
     const SyncWebSocketFactory& socket_factory,
+    const Capabilities* capabilities,
     scoped_ptr<DevToolsHttpClient>* user_client) {
+  scoped_ptr<DeviceMetrics> device_metrics;
+  if (capabilities && capabilities->device_metrics)
+    device_metrics.reset(new DeviceMetrics(*capabilities->device_metrics));
+
   scoped_ptr<DevToolsHttpClient> client(new DevToolsHttpClient(
-      address, context_getter, socket_factory));
+      address, context_getter, socket_factory, device_metrics.Pass()));
   base::TimeTicks deadline =
       base::TimeTicks::Now() + base::TimeDelta::FromSeconds(60);
   Status status = client->Init(deadline - base::TimeTicks::Now());
@@ -194,7 +199,7 @@ Status LaunchExistingChromeSession(
   scoped_ptr<DevToolsHttpClient> devtools_client;
   status = WaitForDevToolsAndCheckVersion(
       capabilities.debugger_address, context_getter, socket_factory,
-      &devtools_client);
+      NULL, &devtools_client);
   if (status.IsError()) {
     return Status(kUnknownError, "cannot connect to chrome at " +
                       capabilities.debugger_address.ToString(),
@@ -278,7 +283,8 @@ Status LaunchDesktopChrome(
 
   scoped_ptr<DevToolsHttpClient> devtools_client;
   status = WaitForDevToolsAndCheckVersion(
-      NetAddress(port), context_getter, socket_factory, &devtools_client);
+      NetAddress(port), context_getter, socket_factory, &capabilities,
+      &devtools_client);
 
   if (status.IsError()) {
     int exit_code;
@@ -378,6 +384,7 @@ Status LaunchAndroidChrome(
   status = WaitForDevToolsAndCheckVersion(NetAddress(port),
                                           context_getter,
                                           socket_factory,
+                                          &capabilities,
                                           &devtools_client);
   if (status.IsError()) {
     device->TearDown();
diff --git a/chrome/test/chromedriver/client/chromedriver.py b/chrome/test/chromedriver/client/chromedriver.py
index 946f85c..063de99 100644
--- a/chrome/test/chromedriver/client/chromedriver.py
+++ b/chrome/test/chromedriver/client/chromedriver.py
@@ -65,7 +65,7 @@ class ChromeDriver(object):
                android_use_running_app=None, chrome_switches=None,
                chrome_extensions=None, chrome_log_path=None,
                debugger_address=None, browser_log_level=None,
-               experimental_options=None):
+               mobile_emulation=None, experimental_options=None):
     self._executor = command_executor.CommandExecutor(server_url)
 
     options = {}
@@ -89,6 +89,10 @@ class ChromeDriver(object):
       assert type(chrome_switches) is list
       options['args'] = chrome_switches
 
+    if mobile_emulation:
+      assert type(mobile_emulation) is dict
+      options['mobileEmulation'] = mobile_emulation
+
     if chrome_extensions:
       assert type(chrome_extensions) is list
       options['extensions'] = chrome_extensions
diff --git a/chrome/test/chromedriver/client/webelement.py b/chrome/test/chromedriver/client/webelement.py
index b3e6a64..5d7dda6 100644
--- a/chrome/test/chromedriver/client/webelement.py
+++ b/chrome/test/chromedriver/client/webelement.py
@@ -25,6 +25,9 @@ class WebElement(object):
     return self._Execute(
         Command.FIND_CHILD_ELEMENTS, {'using': strategy, 'value': target})
 
+  def GetText(self):
+    return self._Execute(Command.GET_ELEMENT_TEXT)
+
   def HoverOver(self):
     self._Execute(Command.HOVER_OVER_ELEMENT)
 
diff --git a/chrome/test/chromedriver/embed_mobile_devices_in_cpp.py b/chrome/test/chromedriver/embed_mobile_devices_in_cpp.py
new file mode 100755
index 0000000..766edce
--- /dev/null
+++ b/chrome/test/chromedriver/embed_mobile_devices_in_cpp.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+# Copyright 2014 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.
+
+"""Embeds standalone JavaScript snippets in C++ code.
+
+The script requires the OverridesView file from WebKit that lists the known
+mobile devices to be passed in as the only argument. The list of known devices
+will be written to a C-style string to be parsed with JSONReader.
+"""
+
+import optparse
+import os
+import sys
+
+import cpp_source
+
+
+def main():
+  parser = optparse.OptionParser()
+  parser.add_option(
+      '', '--directory', type='string', default='.',
+      help='Path to directory where the cc/h files should be created')
+  options, args = parser.parse_args()
+
+  devices = '['
+  file_name = args[0]
+  inside_list = False
+  with open(file_name, 'r') as f:
+    for line in f:
+      if not inside_list:
+        if 'DeviceTab._phones = [' in line or 'DeviceTab._tablets = [' in line:
+          inside_list = True
+      else:
+        if line.strip() == '];':
+          inside_list = False
+          continue
+        devices += line.strip()
+
+  devices += ']'
+  cpp_source.WriteSource('mobile_device_list',
+                         'chrome/test/chromedriver/chrome',
+                         options.directory, {'kMobileDevices': devices})
+
+
+if __name__ == '__main__':
+  sys.exit(main())
diff --git a/chrome/test/chromedriver/session.h b/chrome/test/chromedriver/session.h
index 38c59e2..fe837fb 100644
--- a/chrome/test/chromedriver/session.h
+++ b/chrome/test/chromedriver/session.h
@@ -14,6 +14,7 @@
 #include "base/memory/scoped_vector.h"
 #include "base/time/time.h"
 #include "chrome/test/chromedriver/basic_types.h"
+#include "chrome/test/chromedriver/chrome/device_metrics.h"
 #include "chrome/test/chromedriver/chrome/geoposition.h"
 
 namespace base {
@@ -69,6 +70,7 @@ struct Session {
   base::TimeDelta script_timeout;
   scoped_ptr<std::string> prompt_text;
   scoped_ptr<Geoposition> overridden_geoposition;
+  scoped_ptr<DeviceMetrics> overridden_device_metrics;
   // Logs that populate from DevTools events.
   ScopedVector<WebDriverLog> devtools_logs;
   scoped_ptr<WebDriverLog> driver_log;
diff --git a/chrome/test/chromedriver/session_commands.cc b/chrome/test/chromedriver/session_commands.cc
index b0ad052..864ffd7 100644
--- a/chrome/test/chromedriver/session_commands.cc
+++ b/chrome/test/chromedriver/session_commands.cc
@@ -81,6 +81,8 @@ scoped_ptr<base::DictionaryValue> CreateCapabilities(Chrome* chrome) {
   caps->SetBoolean("handlesAlerts", true);
   caps->SetBoolean("databaseEnabled", false);
   caps->SetBoolean("locationContextEnabled", true);
+  caps->SetBoolean("mobileEmulationEnabled",
+                   chrome->IsMobileEmulationEnabled());
   caps->SetBoolean("applicationCacheEnabled", false);
   caps->SetBoolean("browserConnectionEnabled", false);
   caps->SetBoolean("cssSelectorsEnabled", true);
@@ -99,7 +101,6 @@ scoped_ptr<base::DictionaryValue> CreateCapabilities(Chrome* chrome) {
   return caps.Pass();
 }
 
-
 Status InitSessionHelper(
     const InitSessionParams& bound_params,
     Session* session,
diff --git a/chrome/test/chromedriver/test/run_py_tests.py b/chrome/test/chromedriver/test/run_py_tests.py
index bce431b..1a83bb6 100755
--- a/chrome/test/chromedriver/test/run_py_tests.py
+++ b/chrome/test/chromedriver/test/run_py_tests.py
@@ -100,6 +100,7 @@ _ANDROID_NEGATIVE_FILTER['chrome'] = (
         # Android doesn't support switches and extensions.
         'ChromeSwitchesCapabilityTest.*',
         'ChromeExtensionsCapabilityTest.*',
+        'MobileEmulationCapabilityTest.*',
         # https://crbug.com/274650
         'ChromeDriverTest.testCloseWindow',
         # https://code.google.com/p/chromedriver/issues/detail?id=270
@@ -708,6 +709,9 @@ class ChromeDriverTest(ChromeDriverBaseTest):
   def testDoesntHangOnDebugger(self):
     self._driver.ExecuteScript('debugger;')
 
+  def testMobileEmulationDisabledByDefault(self):
+    self.assertFalse(self._driver.capabilities['mobileEmulationEnabled'])
+
 
 class ChromeDriverAndroidTest(ChromeDriverBaseTest):
   """End to end tests for Android-specific tests."""
@@ -814,6 +818,56 @@ class ChromeLogPathCapabilityTest(ChromeDriverBaseTest):
     self.assertTrue(self.LOG_MESSAGE in open(tmp_log_path.name).read())
 
 
+class MobileEmulationCapabilityTest(ChromeDriverBaseTest):
+  """Tests that ChromeDriver processes chromeOptions.mobileEmulation.
+
+  Makes sure the device metrics are overridden in DevTools and user agent is
+  overridden in Chrome.
+  """
+
+  @staticmethod
+  def GlobalSetUp():
+    def respondWithUserAgentString(request):
+      return request.GetHeader('User-Agent')
+
+    MobileEmulationCapabilityTest._http_server = webserver.WebServer(
+        chrome_paths.GetTestData())
+    MobileEmulationCapabilityTest._http_server.SetCallbackForPath(
+        '/userAgent', respondWithUserAgentString)
+
+  @staticmethod
+  def GlobalTearDown():
+    MobileEmulationCapabilityTest._http_server.Shutdown()
+
+  def testDeviceMetrics(self):
+    driver = self.CreateDriver(
+        mobile_emulation = {
+            'deviceMetrics': {'width': 360, 'height': 640, 'pixelRatio': 3}})
+    self.assertTrue(driver.capabilities['mobileEmulationEnabled'])
+    self.assertEqual(360, driver.ExecuteScript('return window.innerWidth'))
+    self.assertEqual(640, driver.ExecuteScript('return window.innerHeight'))
+
+  def testUserAgent(self):
+    driver = self.CreateDriver(
+        mobile_emulation = {'userAgent': 'Agent Smith'})
+    driver.Load(self._http_server.GetUrl() + '/userAgent')
+    body_tag = driver.FindElement('tag name', 'body')
+    self.assertEqual("Agent Smith", body_tag.GetText())
+
+  def testDeviceName(self):
+    driver = self.CreateDriver(
+        mobile_emulation = {'deviceName': 'Google Nexus 5'})
+    driver.Load(self._http_server.GetUrl() + '/userAgent')
+    self.assertEqual(360, driver.ExecuteScript('return window.innerWidth'))
+    self.assertEqual(640, driver.ExecuteScript('return window.innerHeight'))
+    body_tag = driver.FindElement('tag name', 'body')
+    self.assertEqual(
+        'Mozilla/5.0 (Linux; Android 4.2.1; en-us; Nexus 5 Build/JOP40D) AppleW'
+        'ebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.166 Mobile Safari/53'
+        '5.19',
+        body_tag.GetText())
+
+
 class ChromeDriverLogTest(unittest.TestCase):
   """Tests that chromedriver produces the expected log file."""
 
@@ -1007,6 +1061,8 @@ if __name__ == '__main__':
       sys.modules[__name__])
   tests = unittest_util.FilterTestSuite(all_tests_suite, options.filter)
   ChromeDriverTest.GlobalSetUp()
+  MobileEmulationCapabilityTest.GlobalSetUp()
   result = unittest.TextTestRunner(stream=sys.stdout, verbosity=2).run(tests)
   ChromeDriverTest.GlobalTearDown()
+  MobileEmulationCapabilityTest.GlobalTearDown()
   sys.exit(len(result.failures) + len(result.errors))
diff --git a/chrome/test/chromedriver/test/webserver.py b/chrome/test/chromedriver/test/webserver.py
index 716e0f4..9de0339 100644
--- a/chrome/test/chromedriver/test/webserver.py
+++ b/chrome/test/chromedriver/test/webserver.py
@@ -48,6 +48,9 @@ class Request(object):
   def GetPath(self):
     return self._handler.path
 
+  def GetHeader(self, name):
+    return self._handler.headers.getheader(name)
+
 
 class _BaseServer(BaseHTTPServer.HTTPServer):
   """Internal server that throws if timed out waiting for a request."""
@@ -120,19 +123,28 @@ class WebServer(object):
     self._thread.daemon = True
     self._thread.start()
     self._path_data_map = {}
-    self._path_data_lock = threading.Lock()
+    self._path_callback_map = {}
+    self._path_maps_lock = threading.Lock()
 
   def _OnRequest(self, request, responder):
     path = request.GetPath().split('?')[0]
 
-    # Serve from path -> data map.
-    self._path_data_lock.acquire()
+    # Serve from path -> callback and data maps.
+    self._path_maps_lock.acquire()
     try:
+      if path in self._path_callback_map:
+        body = self._path_callback_map[path](request)
+        if body:
+          responder.SendResponse(body)
+        else:
+          responder.SendError(503)
+        return
+
       if path in self._path_data_map:
         responder.SendResponse(self._path_data_map[path])
         return
     finally:
-      self._path_data_lock.release()
+      self._path_maps_lock.release()
 
     # Serve from file.
     path = os.path.normpath(
@@ -146,11 +158,19 @@ class WebServer(object):
     responder.SendResponseFromFile(path)
 
   def SetDataForPath(self, path, data):
-    self._path_data_lock.acquire()
+    self._path_maps_lock.acquire()
     try:
       self._path_data_map[path] = data
     finally:
-      self._path_data_lock.release()
+      self._path_maps_lock.release()
+
+  def SetCallbackForPath(self, path, func):
+    self._path_maps_lock.acquire()
+    try:
+      self._path_callback_map[path] = func
+    finally:
+      self._path_maps_lock.release()
+
 
   def GetUrl(self):
     """Returns the base URL of the server."""