DevTools: Tests for DevToolsAndroidBridge device polling

chrome/browser/devtools/device/usb/android_usb_browsertest.cc

+// 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 <algorithm>
+
+#include "base/strings/utf_string_conversions.h"
+#include "chrome/browser/devtools/device/devtools_android_bridge.h"
+#include "chrome/browser/devtools/device/usb/android_usb_device.h"
+#include "chrome/browser/devtools/device/usb/usb_device_provider.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "components/usb_service/usb_device.h"
+#include "components/usb_service/usb_device_handle.h"
+#include "components/usb_service/usb_interface.h"
+#include "components/usb_service/usb_service.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/test/test_utils.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using content::BrowserThread;
+using namespace usb_service;
+
+namespace {
+
+struct AndroidTraits {
+  static const int kClass = 0xff;
+  static const int kSubclass = 0x42;
+  static const int kProtocol = 0x1;
+};
+
+struct NonAndroidTraits {
+  static const int kClass = 0xf0;
+  static const int kSubclass = 0x42;
+  static const int kProtocol = 0x2;
+};
+
+const uint32 kMaxPayload = 4096;
+const uint32 kVersion = 0x01000000;
+
+const char kOpenedUnixSocketsCommand[] = "shell:cat /proc/net/unix";
+const char kDeviceModelCommand[] = "shell:getprop ro.product.model";
+const char kDumpsysCommand[] = "shell:dumpsys window policy";
+const char kListProcessesCommand[] = "shell:ps";
+const char kInstalledChromePackagesCommand[] = "shell:pm list packages";
+const char kDeviceModel[] = "Nexus 5";
+const char kDeviceSerial[] = "Sample serial";
+
+const char kSampleOpenedUnixSockets[] =
+    "Num       RefCount Protocol Flags    Type St Inode Path\n"
+    "00000000: 00000004 00000000"
+    " 00000000 0002 01  3328 /dev/socket/wpa_wlan0\n"
+    "00000000: 00000002 00000000"
+    " 00010000 0001 01  5394 /dev/socket/vold\n";
+
+const char kSampleListProcesses[] =
+    "USER   PID  PPID VSIZE  RSS    WCHAN    PC         NAME\n"
+    "root   1    0    688    508    ffffffff 00000000 S /init\r\n"
+    "u0_a75 2425 123  933736 193024 ffffffff 00000000 S com.sample.feed\r\n"
+    "nfc    741  123  706448 26316  ffffffff 00000000 S com.android.nfc\r\n"
+    "u0_a76 1001 124  111111 222222 ffffffff 00000000 S com.android.chrome\r\n"
+    "u0_a78 1003 126  111111 222222 ffffffff 00000000 S com.noprocess.app\r\n";
+
+const char kSampleListPackages[] =
+    "package:com.sample.feed\r\n"
+    "package:com.android.nfc\r\n"
+    "package:com.android.chrome\r\n"
+    "package:com.chrome.beta\r\n"
+    "package:com.google.android.apps.chrome\r\n";
+
+const char kSampleDumpsys[] =
+    "WINDOW MANAGER POLICY STATE (dumpsys window policy)\r\n"
+    "    mSafeMode=false mSystemReady=true mSystemBooted=true\r\n"
+    "    mStable=(0,50)-(720,1184)\r\n"  // Only mStable parameter is parsed
+    "    mForceStatusBar=false mForceStatusBarFromKeyguard=false\r\n";
+
+const char* GetMockShellResponse(std::string command) {
+  if (command == kDeviceModelCommand) {
+    return kDeviceModel;
+  } else if (command == kOpenedUnixSocketsCommand) {
+    return kSampleOpenedUnixSockets;
+  } else if (command == kDumpsysCommand) {
+    return kSampleDumpsys;
+  } else if (command == kListProcessesCommand) {
+    return kSampleListProcesses;
+  } else if (command == kInstalledChromePackagesCommand) {
+    return kSampleListPackages;
+  }
+
+  DCHECK(false) << "Should not be reached";
+
+  return "";
+}
+
+class MockUsbEndpointDescriptor : public UsbEndpointDescriptor {
+ public:
+  virtual int GetAddress() const OVERRIDE { return address_; }
+
+  virtual UsbEndpointDirection GetDirection() const OVERRIDE {
+    return direction_;
+  }
+
+  virtual int GetMaximumPacketSize() const OVERRIDE {
+    return maximum_packet_size_;
+  }
+
+  virtual UsbSynchronizationType GetSynchronizationType() const OVERRIDE {
+    return usb_synchronization_type_;
+  }
+
+  virtual UsbTransferType GetTransferType() const OVERRIDE {
+    return usb_transfer_type_;
+  }
+  virtual UsbUsageType GetUsageType() const OVERRIDE { return usb_usage_type_; }
+
+  virtual int GetPollingInterval() const OVERRIDE { return polling_interval_; }
+
+  int address_;
+  UsbEndpointDirection direction_;
+  int maximum_packet_size_;
+  UsbSynchronizationType usb_synchronization_type_;
+  UsbTransferType usb_transfer_type_;
+  UsbUsageType usb_usage_type_;
+  int polling_interval_;
+
+ private:
+  virtual ~MockUsbEndpointDescriptor() {}
+};
+
+template <class T>
+class MockUsbInterfaceAltSettingDescriptor
+    : public UsbInterfaceAltSettingDescriptor {
+ public:
+  MockUsbInterfaceAltSettingDescriptor(int interface_number,
+                                       int alternate_setting)
+      : interface_number_(interface_number),
+        alternate_setting_(alternate_setting) {}
+
+  virtual size_t GetNumEndpoints() const OVERRIDE {
+    // See IsAndroidInterface function in android_usb_device.cc
+    return 2;
+  }
+
+  virtual scoped_refptr<const UsbEndpointDescriptor> GetEndpoint(
+      size_t index) const OVERRIDE {
+    EXPECT_GT(static_cast<size_t>(2), index);
+    MockUsbEndpointDescriptor* result = new MockUsbEndpointDescriptor();
+    result->address_ = index + 1;
+    result->usb_transfer_type_ = USB_TRANSFER_BULK;
+    result->direction_ =
+        ((index == 0) ? USB_DIRECTION_INBOUND : USB_DIRECTION_OUTBOUND);
+    result->maximum_packet_size_ = 1 << 20;  // 1Mb maximum packet size
+    return result;
+  }
+
+  virtual int GetInterfaceNumber() const OVERRIDE { return interface_number_; }
+
+  virtual int GetAlternateSetting() const OVERRIDE {
+    return alternate_setting_;
+  }
+
+  virtual int GetInterfaceClass() const OVERRIDE { return T::kClass; }
+
+  virtual int GetInterfaceSubclass() const OVERRIDE { return T::kSubclass; }
+
+  virtual int GetInterfaceProtocol() const OVERRIDE { return T::kProtocol; }
+
+ protected:
+  virtual ~MockUsbInterfaceAltSettingDescriptor() {};
+
+ private:
+  const int interface_number_;
+  const int alternate_setting_;
+};
+
+template <class T>
+class MockUsbInterfaceDescriptor : public UsbInterfaceDescriptor {
+ public:
+  explicit MockUsbInterfaceDescriptor(int interface_number)
+      : interface_number_(interface_number) {}
+
+  virtual size_t GetNumAltSettings() const OVERRIDE {
+    // See IsAndroidInterface function in android_usb_device.cc
+    return 1;
+  }
+  virtual scoped_refptr<const UsbInterfaceAltSettingDescriptor> GetAltSetting(
+      size_t index) const OVERRIDE {
+    EXPECT_EQ(static_cast<size_t>(0), index);
+    return new MockUsbInterfaceAltSettingDescriptor<T>(interface_number_, 0);
+  }
+
+ protected:
+  const int interface_number_;
+  virtual ~MockUsbInterfaceDescriptor() {}
+};
+
+template <class T>
+class MockUsbConfigDescriptor : public UsbConfigDescriptor {
+ public:
+  MockUsbConfigDescriptor() {}
+
+  virtual size_t GetNumInterfaces() const OVERRIDE { return 1; }
+
+  virtual scoped_refptr<const UsbInterfaceDescriptor> GetInterface(
+      size_t index) const OVERRIDE {
+    EXPECT_EQ(static_cast<size_t>(0), index);
+    return new MockUsbInterfaceDescriptor<T>(index);
+  }
+
+ protected:
+  virtual ~MockUsbConfigDescriptor() {};
+};
+
+template <class T>
+class MockUsbDevice;
+
+template <class T>
+class MockUsbDeviceHandle : public UsbDeviceHandle {
+ public:
+  explicit MockUsbDeviceHandle(MockUsbDevice<T>* device)
+      : device_(device),
+        remaining_body_length_(0),
+        next_local_socket_(0) {}
+
+  virtual scoped_refptr<UsbDevice> GetDevice() const OVERRIDE {
+    return device_;
+  }
+
+  virtual void Close() OVERRIDE { device_ = NULL; }
+
+  bool ClaimInterface(const int interface_number) {
+    if (device_->claimed_interfaces_.find(interface_number) !=
+        device_->claimed_interfaces_.end())
+      return false;
+
+    device_->claimed_interfaces_.insert(interface_number);
+    return true;
+  }
+
+  bool ReleaseInterface(const int interface_number) {
+    if (device_->claimed_interfaces_.find(interface_number) ==
+        device_->claimed_interfaces_.end())
+      return false;
+
+    device_->claimed_interfaces_.erase(interface_number);
+    return true;
+  }
+
+  virtual bool SetInterfaceAlternateSetting(
+      const int interface_number,
+      const int alternate_setting) OVERRIDE {
+    return true;
+  }
+
+  virtual bool ResetDevice() OVERRIDE { return true; }
+
+  virtual bool GetSerial(base::string16* serial) OVERRIDE {
+    *serial = base::UTF8ToUTF16(kDeviceSerial);
+    return true;
+  }
+
+  // Async IO. Can be called on any thread.
+  virtual void ControlTransfer(const UsbEndpointDirection direction,
+                               const TransferRequestType request_type,
+                               const TransferRecipient recipient,
+                               const uint8 request,
+                               const uint16 value,
+                               const uint16 index,
+                               net::IOBuffer* buffer,
+                               const size_t length,
+                               const unsigned int timeout,
+                               const UsbTransferCallback& callback) OVERRIDE {}
+
+  virtual void BulkTransfer(const UsbEndpointDirection direction,
+                            const uint8 endpoint,
+                            net::IOBuffer* buffer,
+                            const size_t length,
+                            const unsigned int timeout,
+                            const UsbTransferCallback& callback) OVERRIDE {
+    if (direction == USB_DIRECTION_OUTBOUND) {
+      if (remaining_body_length_ == 0) {
+        std::vector<uint32> header(6);
+        memcpy(&header[0], buffer->data(), length);
+        current_message_ = new AdbMessage(header[0], header[1], header[2], "");
+        remaining_body_length_ = header[3];
+        uint32 magic = header[5];
+        if ((current_message_->command ^ 0xffffffff) != magic) {
+          DCHECK(false) << "Header checksum error";
+          return;
+        }
+      } else {
+        DCHECK(current_message_);
+        current_message_->body += std::string(buffer->data(), length);
+        remaining_body_length_ -= length;
+      }
+
+      if (remaining_body_length_ == 0) {
+        ProcessIncoming();
+      }
+
+      base::MessageLoop::current()->PostTask(
+          FROM_HERE,
+          base::Bind(callback,
+                     usb_service::USB_TRANSFER_COMPLETED,
+                     scoped_refptr<net::IOBuffer>(),
+                     0));
+
+    } else if (direction == USB_DIRECTION_INBOUND) {
+      queries_.push(Query(callback, make_scoped_refptr(buffer), length));
+      ProcessQueries();
+    }
+  }
+
+  template <class D>
+  void append(D data) {
+    std::copy(reinterpret_cast<char*>(&data),
+              (reinterpret_cast<char*>(&data)) + sizeof(D),
+              std::back_inserter(output_buffer_));
+  }
+
+  // Copied from AndroidUsbDevice::Checksum
+  uint32 Checksum(const std::string& data) {
+    unsigned char* x = (unsigned char*)data.data();
+    int count = data.length();
+    uint32 sum = 0;
+    while (count-- > 0)
+      sum += *x++;
+    return sum;
+  }
+
+  void ProcessIncoming() {
+    DCHECK(current_message_);
+    switch (current_message_->command) {
+      case AdbMessage::kCommandCNXN:
+        WriteResponse(new AdbMessage(AdbMessage::kCommandCNXN,
+                                     kVersion,
+                                     kMaxPayload,
+                                     "device::ro.product.name=SampleProduct;ro."
+                                     "product.model=SampleModel;ro.product."
+                                     "device=SampleDevice;"));
+        break;
+      case AdbMessage::kCommandOPEN:
+        DCHECK(current_message_->arg1 == 0);
+        DCHECK(current_message_->arg0 != 0);
+        if (current_message_->body.find("shell:") != std::string::npos) {
+          WriteResponse(new AdbMessage(AdbMessage::kCommandOKAY,
+                                       ++next_local_socket_,
+                                       current_message_->arg0,
+                                       ""));
+          WriteResponse(
+              new AdbMessage(AdbMessage::kCommandWRTE,
+                             next_local_socket_,
+                             current_message_->arg0,
+                             GetMockShellResponse(current_message_->body.substr(
+                                 0, current_message_->body.size() - 1))));
+          WriteResponse(new AdbMessage(
+              AdbMessage::kCommandCLSE, 0, current_message_->arg0, ""));
+        }
+      default:
+        return;
+    }
+    ProcessQueries();
+  }
+
+  void WriteResponse(scoped_refptr<AdbMessage> response) {
+    append(response->command);
+    append(response->arg0);
+    append(response->arg1);
+    bool add_zero = response->body.length() &&
+                    (response->command != AdbMessage::kCommandWRTE);
+    append(static_cast<uint32>(response->body.length() + (add_zero ? 1 : 0)));
+    append(Checksum(response->body));
+    append(response->command ^ 0xffffffff);
+    std::copy(response->body.begin(),
+              response->body.end(),
+              std::back_inserter(output_buffer_));
+    if (add_zero) {
+      output_buffer_.push_back(0);
+    }
+    ProcessQueries();
+  }
+
+  void ProcessQueries() {
+    if (!queries_.size())
+      return;
+    Query query = queries_.front();
+
+    if (query.size > output_buffer_.size())
+      return;
+
+    queries_.pop();
+    std::copy(output_buffer_.begin(),
+              output_buffer_.begin() + query.size,
+              query.buffer->data());
+    output_buffer_.erase(output_buffer_.begin(),
+                         output_buffer_.begin() + query.size);
+    base::MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(query.callback,
+                   usb_service::USB_TRANSFER_COMPLETED,
+                   query.buffer,
+                   query.size));
+  }
+
+  virtual void InterruptTransfer(const UsbEndpointDirection direction,
+                                 const uint8 endpoint,
+                                 net::IOBuffer* buffer,
+                                 const size_t length,
+                                 const unsigned int timeout,
+                                 const UsbTransferCallback& callback) OVERRIDE {
+  }
+
+  virtual void IsochronousTransfer(
+      const UsbEndpointDirection direction,
+      const uint8 endpoint,
+      net::IOBuffer* buffer,
+      const size_t length,
+      const unsigned int packets,
+      const unsigned int packet_length,
+      const unsigned int timeout,
+      const UsbTransferCallback& callback) OVERRIDE {}
+
+ protected:
+  virtual ~MockUsbDeviceHandle() {}
+
+  struct Query {
+    UsbTransferCallback callback;
+    scoped_refptr<net::IOBuffer> buffer;
+    size_t size;
+
+    Query(UsbTransferCallback callback,
+          scoped_refptr<net::IOBuffer> buffer,
+          int size)
+        : callback(callback), buffer(buffer), size(size) {};
+  };
+
+  scoped_refptr<MockUsbDevice<T> > device_;
+  uint32 remaining_body_length_;
+  scoped_refptr<AdbMessage> current_message_;
+  std::vector<char> output_buffer_;
+  std::queue<Query> queries_;
+  int next_local_socket_;
+};
+
+template <class T>
+class MockUsbDevice : public UsbDevice {
+ public:
+  MockUsbDevice() : UsbDevice(0, 0, 0) {}
+
+  virtual scoped_refptr<UsbDeviceHandle> Open() OVERRIDE {
+    return new MockUsbDeviceHandle<T>(this);
+  }
+
+  virtual scoped_refptr<UsbConfigDescriptor> ListInterfaces() OVERRIDE {
+    return new MockUsbConfigDescriptor<T>();
+  }
+
+  virtual bool Close(scoped_refptr<UsbDeviceHandle> handle) OVERRIDE {
+    return true;
+  }
+
+#if defined(OS_CHROMEOS)
+  // On ChromeOS, if an interface of a claimed device is not claimed, the
+  // permission broker can change the owner of the device so that the unclaimed
+  // interfaces can be used. If this argument is missing, permission broker will
+  // not be used and this method fails if the device is claimed.
+  virtual void RequestUsbAcess(
+      int interface_id,
+      const base::Callback<void(bool success)>& callback) OVERRIDE {
+    callback.Run(true);
+  }
+#endif  // OS_CHROMEOS
+
+  std::set<int> claimed_interfaces_;
+
+ protected:
+  virtual ~MockUsbDevice() {}
+};
+
+class MockUsbService : public UsbService {
+ public:
+  MockUsbService() {
+    devices_.push_back(new MockUsbDevice<AndroidTraits>());
+  }
+
+  virtual ~MockUsbService() {}
+
+  virtual scoped_refptr<UsbDevice> GetDeviceById(uint32 unique_id) OVERRIDE {
+    NOTIMPLEMENTED();
+    return NULL;
+  }
+
+  virtual void GetDevices(
+      std::vector<scoped_refptr<UsbDevice> >* devices) OVERRIDE {
+    STLClearObject(devices);
+    std::copy(devices_.begin(), devices_.end(), back_inserter(*devices));
+  }
+
+  std::vector<scoped_refptr<UsbDevice> > devices_;
+};
+
+class MockUsbServiceForCheckingTraits : public UsbService {
+ public:
+  MockUsbServiceForCheckingTraits() : step_(0) {}
+
+  virtual ~MockUsbServiceForCheckingTraits() {}
+
+  virtual scoped_refptr<UsbDevice> GetDeviceById(uint32 unique_id) OVERRIDE {
+    NOTIMPLEMENTED();
+    return NULL;
+  }
+
+  virtual void GetDevices(
+      std::vector<scoped_refptr<UsbDevice> >* devices) OVERRIDE {
+    STLClearObject(devices);
+    // This switch should be kept in sync with
+    // AndroidUsbBrowserTest::DeviceCountChanged.
+    switch (step_) {
+      case 0:
+        // No devices.
+        break;
+      case 1:
+        // Android device.
+        devices->push_back(new MockUsbDevice<AndroidTraits>());
+        break;
+      case 2:
+        // Android and non-android device.
+        devices->push_back(new MockUsbDevice<AndroidTraits>());
+        devices->push_back(new MockUsbDevice<NonAndroidTraits>());
+        break;
+      case 3:
+        // Non-android device.
+        devices->push_back(new MockUsbDevice<NonAndroidTraits>());
+        break;
+    }
+    step_++;
+  }
+
+ private:
+  int step_;
+};
+
+class DevToolsAndroidBridgeWarmUp
+    : public DevToolsAndroidBridge::DeviceCountListener {
+ public:
+  DevToolsAndroidBridgeWarmUp(base::Closure closure,
+                              scoped_refptr<DevToolsAndroidBridge> adb_bridge)
+      : closure_(closure), adb_bridge_(adb_bridge) {}
+
+  virtual void DeviceCountChanged(int count) OVERRIDE {
+    adb_bridge_->RemoveDeviceCountListener(this);
+    closure_.Run();
+  }
+
+  base::Closure closure_;
+  scoped_refptr<DevToolsAndroidBridge> adb_bridge_;
+};
+
+class AndroidUsbDiscoveryTest : public InProcessBrowserTest {
+ protected:
+  AndroidUsbDiscoveryTest()
+      : scheduler_invoked_(0) {
+  }
+  virtual void SetUpOnMainThread() OVERRIDE {
+    scoped_refptr<content::MessageLoopRunner> runner =
+        new content::MessageLoopRunner;
+
+    BrowserThread::PostTaskAndReply(
+        BrowserThread::FILE,
+        FROM_HERE,
+        base::Bind(&AndroidUsbDiscoveryTest::SetUpService, this),
+        runner->QuitClosure());
+    runner->Run();
+
+    adb_bridge_ =
+        DevToolsAndroidBridge::Factory::GetForProfile(browser()->profile());
+    DCHECK(adb_bridge_);
+    adb_bridge_->set_task_scheduler_for_test(base::Bind(
+        &AndroidUsbDiscoveryTest::ScheduleDeviceCountRequest, this));
+
+    scoped_refptr<UsbDeviceProvider> provider =
+        new UsbDeviceProvider(browser()->profile());
+
+    AndroidDeviceManager::DeviceProviders providers;
+    providers.push_back(provider);
+    adb_bridge_->set_device_providers_for_test(providers);
+    runner_ = new content::MessageLoopRunner;
+  }
+
+  void ScheduleDeviceCountRequest(const base::Closure& request) {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    scheduler_invoked_++;
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, request);
+  }
+
+  virtual void SetUpService() {
+    UsbService::SetInstanceForTest(new MockUsbService());
+  }
+
+  virtual void CleanUpOnMainThread() OVERRIDE {
+    scoped_refptr<content::MessageLoopRunner> runner =
+        new content::MessageLoopRunner;
+    UsbService* service = NULL;
+    BrowserThread::PostTaskAndReply(
+        BrowserThread::FILE,
+        FROM_HERE,
+        base::Bind(&UsbService::SetInstanceForTest, service),
+        runner->QuitClosure());
+    runner->Run();
+  }
+
+  scoped_refptr<content::MessageLoopRunner> runner_;
+  scoped_refptr<DevToolsAndroidBridge> adb_bridge_;
+  int scheduler_invoked_;
+};
+
+class AndroidUsbCountTest : public AndroidUsbDiscoveryTest {
+ protected:
+  virtual void SetUpOnMainThread() OVERRIDE {
+    AndroidUsbDiscoveryTest::SetUpOnMainThread();
+    DevToolsAndroidBridgeWarmUp warmup(runner_->QuitClosure(), adb_bridge_);
+    adb_bridge_->AddDeviceCountListener(&warmup);
+    runner_->Run();
+    runner_ = new content::MessageLoopRunner;
+  }
+};
+
+class AndroidUsbTraitsTest : public AndroidUsbDiscoveryTest {
+ protected:
+  virtual void SetUpService() OVERRIDE {
+    UsbService::SetInstanceForTest(new MockUsbServiceForCheckingTraits());
+  }
+};
+
+class MockListListener : public DevToolsAndroidBridge::DeviceListListener {
+ public:
+  MockListListener(scoped_refptr<DevToolsAndroidBridge> adb_bridge,
+                   const base::Closure& callback)
+      : adb_bridge_(adb_bridge),
+        callback_(callback) {
+  }
+
+  virtual void DeviceListChanged(
+      const DevToolsAndroidBridge::RemoteDevices& devices) OVERRIDE {
+    if (devices.size() > 0) {
+      if (devices[0]->is_connected()) {
+        ASSERT_EQ(kDeviceModel, devices[0]->model());
+        ASSERT_EQ(kDeviceSerial, devices[0]->serial());
+        adb_bridge_->RemoveDeviceListListener(this);
+        callback_.Run();
+      }
+    }
+  }
+
+  scoped_refptr<DevToolsAndroidBridge> adb_bridge_;
+  base::Closure callback_;
+};
+
+class MockCountListener : public DevToolsAndroidBridge::DeviceCountListener {
+ public:
+  explicit MockCountListener(scoped_refptr<DevToolsAndroidBridge> adb_bridge)
+      : adb_bridge_(adb_bridge),
+        reposts_left_(10),
+        invoked_(0) {
+  }
+
+  virtual void DeviceCountChanged(int count) OVERRIDE {
+    ++invoked_;
+    adb_bridge_->RemoveDeviceCountListener(this);
+    Shutdown();
+  }
+
+  void Shutdown() {
+    ShutdownOnUIThread();
+  };
+
+  void ShutdownOnUIThread() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+    if (reposts_left_-- == 0) {
+      base::MessageLoop::current()->Quit();
+    } else {
+      BrowserThread::PostTask(
+          BrowserThread::FILE,
+          FROM_HERE,
+          base::Bind(&MockCountListener::ShutdownOnFileThread,
+                     base::Unretained(this)));
+    }
+  }
+
+  void ShutdownOnFileThread() {
+    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+    BrowserThread::PostTask(BrowserThread::UI,
+                            FROM_HERE,
+                            base::Bind(&MockCountListener::ShutdownOnUIThread,
+                                       base::Unretained(this)));
+  }
+
+  scoped_refptr<DevToolsAndroidBridge> adb_bridge_;
+  int reposts_left_;
+  int invoked_;
+};
+
+class MockCountListenerWithReAdd : public MockCountListener {
+ public:
+  explicit MockCountListenerWithReAdd(
+      scoped_refptr<DevToolsAndroidBridge> adb_bridge)
+      : MockCountListener(adb_bridge),
+        readd_count_(2) {
+  }
+
+  virtual void DeviceCountChanged(int count) OVERRIDE {
+    ++invoked_;
+    adb_bridge_->RemoveDeviceCountListener(this);
+    if (readd_count_ > 0) {
+      readd_count_--;
+      adb_bridge_->AddDeviceCountListener(this);
+      adb_bridge_->RemoveDeviceCountListener(this);
+      adb_bridge_->AddDeviceCountListener(this);
+    } else {
+      Shutdown();
+    }
+  }
+
+  int readd_count_;
+};
+
+class MockCountListenerWithReAddWhileQueued : public MockCountListener {
+ public:
+  MockCountListenerWithReAddWhileQueued(
+      scoped_refptr<DevToolsAndroidBridge> adb_bridge)
+      : MockCountListener(adb_bridge),
+        readded_(false) {
+  }
+
+  virtual void DeviceCountChanged(int count) OVERRIDE {
+    ++invoked_;
+    if (!readded_) {
+      readded_ = true;
+      base::MessageLoop::current()->PostTask(
+          FROM_HERE,
+          base::Bind(&MockCountListenerWithReAddWhileQueued::ReAdd,
+                     base::Unretained(this)));
+    } else {
+      adb_bridge_->RemoveDeviceCountListener(this);
+      Shutdown();
+    }
+  }
+
+  void ReAdd() {
+    adb_bridge_->RemoveDeviceCountListener(this);
+    adb_bridge_->AddDeviceCountListener(this);
+  }
+
+  bool readded_;
+};
+
+class MockCountListenerForCheckingTraits : public MockCountListener {
+ public:
+  MockCountListenerForCheckingTraits(
+      scoped_refptr<DevToolsAndroidBridge> adb_bridge)
+      : MockCountListener(adb_bridge),
+        step_(0) {
+  }
+  virtual void DeviceCountChanged(int count) OVERRIDE {
+    switch (step_) {
+      case 0:
+        // Check for 0 devices when no devices present.
+        EXPECT_EQ(0, count);
+        break;
+      case 1:
+        // Check for 1 device when only android device present.
+        EXPECT_EQ(1, count);
+        break;
+      case 2:
+        // Check for 1 device when android and non-android devices present.
+        EXPECT_EQ(1, count);
+        break;
+      case 3:
+        // Check for 0 devices when only non-android devices present.
+        EXPECT_EQ(0, count);
+        adb_bridge_->RemoveDeviceCountListener(this);
+        Shutdown();
+        break;
+      default:
+        EXPECT_TRUE(false) << "Unknown step " << step_;
+    }
+    step_++;
+  }
+
+  int step_;
+};
+
+}  // namespace
+
+IN_PROC_BROWSER_TEST_F(AndroidUsbDiscoveryTest, TestDeviceDiscovery) {
+  MockListListener listener(adb_bridge_, runner_->QuitClosure());
+  adb_bridge_->AddDeviceListListener(&listener);
+  runner_->Run();
+}
+
+IN_PROC_BROWSER_TEST_F(AndroidUsbCountTest,
+                       TestNoMultipleCallsRemoveInCallback) {
+  MockCountListener listener(adb_bridge_);
+  adb_bridge_->AddDeviceCountListener(&listener);
+  runner_->Run();
+  EXPECT_EQ(1, listener.invoked_);
+  EXPECT_EQ(listener.invoked_ - 1, scheduler_invoked_);
+}
+
+IN_PROC_BROWSER_TEST_F(AndroidUsbCountTest,
+                       TestNoMultipleCallsRemoveAddInCallback) {
+  MockCountListenerWithReAdd listener(adb_bridge_);
+  adb_bridge_->AddDeviceCountListener(&listener);
+  runner_->Run();
+  EXPECT_EQ(3, listener.invoked_);
+  EXPECT_EQ(listener.invoked_ - 1, scheduler_invoked_);
+}
+
+IN_PROC_BROWSER_TEST_F(AndroidUsbCountTest,
+                       TestNoMultipleCallsRemoveAddOnStart) {
+  MockCountListener listener(adb_bridge_);
+  adb_bridge_->AddDeviceCountListener(&listener);
+  adb_bridge_->RemoveDeviceCountListener(&listener);
+  adb_bridge_->AddDeviceCountListener(&listener);
+  runner_->Run();
+  EXPECT_EQ(1, listener.invoked_);
+  EXPECT_EQ(listener.invoked_ - 1, scheduler_invoked_);
+}
+
+IN_PROC_BROWSER_TEST_F(AndroidUsbCountTest,
+                       TestNoMultipleCallsRemoveAddWhileQueued) {
+  MockCountListenerWithReAddWhileQueued listener(adb_bridge_);
+  adb_bridge_->AddDeviceCountListener(&listener);
+  runner_->Run();
+  EXPECT_EQ(2, listener.invoked_);
+  EXPECT_EQ(listener.invoked_ - 1, scheduler_invoked_);
+}
+
+IN_PROC_BROWSER_TEST_F(AndroidUsbTraitsTest, TestDeviceCounting) {
+  MockCountListenerForCheckingTraits listener(adb_bridge_);
+  adb_bridge_->AddDeviceCountListener(&listener);
+  runner_->Run();
+}