Mojo C++ bindings: make Array/Map/String non-null by default.

Array<X> a;  // Default construct an empty array.
Array<X> b(nullptr);  // Construct a null array.

a.clear();  // Set to an empty array.
a = nullptr;  // Set to a null array.

BUG=579634
TEST=None

Review URL: https://codereview.chromium.org/1693943002

Cr-Commit-Position: refs/heads/master@{#375304}

4 files changed, 6 insertions, 6 deletions

diff --git a/device/serial/serial_device_enumerator_linux.cc b/device/serial/serial_device_enumerator_linux.cc
index d4af830..b4de00c 100644
--- a/device/serial/serial_device_enumerator_linux.cc
+++ b/device/serial/serial_device_enumerator_linux.cc
@@ -36,7 +36,7 @@ SerialDeviceEnumeratorLinux::SerialDeviceEnumeratorLinux() {
 SerialDeviceEnumeratorLinux::~SerialDeviceEnumeratorLinux() {}
 
 mojo::Array<serial::DeviceInfoPtr> SerialDeviceEnumeratorLinux::GetDevices() {
-  mojo::Array<serial::DeviceInfoPtr> devices(0);
+  mojo::Array<serial::DeviceInfoPtr> devices;
   ScopedUdevEnumeratePtr enumerate(udev_enumerate_new(udev_.get()));
   if (!enumerate) {
     LOG(ERROR) << "Serial device enumeration failed.";
diff --git a/device/serial/serial_device_enumerator_mac.cc b/device/serial/serial_device_enumerator_mac.cc
index 7854c99..ff0b5fa 100644
--- a/device/serial/serial_device_enumerator_mac.cc
+++ b/device/serial/serial_device_enumerator_mac.cc
@@ -101,7 +101,7 @@ int Clamp(int value, int min, int max) {
 // enumerating serial devices (IOKit).  This new method gives more information
 // about the devices than the old method.
 mojo::Array<serial::DeviceInfoPtr> GetDevicesNew() {
-  mojo::Array<serial::DeviceInfoPtr> devices(0);
+  mojo::Array<serial::DeviceInfoPtr> devices;
 
   // Make a service query to find all serial devices.
   CFMutableDictionaryRef matchingDict =
@@ -180,7 +180,7 @@ mojo::Array<serial::DeviceInfoPtr> GetDevicesOld() {
   valid_patterns.insert("/dev/tty.*");
   valid_patterns.insert("/dev/cu.*");
 
-  mojo::Array<serial::DeviceInfoPtr> devices(0);
+  mojo::Array<serial::DeviceInfoPtr> devices;
   base::FileEnumerator enumerator(kDevRoot, false, kFilesAndSymLinks);
   do {
     const base::FilePath next_device_path(enumerator.Next());
diff --git a/device/serial/serial_device_enumerator_win.cc b/device/serial/serial_device_enumerator_win.cc
index 79c4001..2e83fd6 100644
--- a/device/serial/serial_device_enumerator_win.cc
+++ b/device/serial/serial_device_enumerator_win.cc
@@ -87,7 +87,7 @@ int Clamp(int value, int min, int max) {
 // enumerating serial devices (SetupDi).  This new method gives more information
 // about the devices than the old method.
 mojo::Array<serial::DeviceInfoPtr> GetDevicesNew() {
-  mojo::Array<serial::DeviceInfoPtr> devices(0);
+  mojo::Array<serial::DeviceInfoPtr> devices;
 
   // Make a device interface query to find all serial devices.
   HDEVINFO dev_info =
@@ -141,7 +141,7 @@ mojo::Array<serial::DeviceInfoPtr> GetDevicesNew() {
 mojo::Array<serial::DeviceInfoPtr> GetDevicesOld() {
   base::win::RegistryValueIterator iter_key(
       HKEY_LOCAL_MACHINE, L"HARDWARE\\DEVICEMAP\\SERIALCOMM\\");
-  mojo::Array<serial::DeviceInfoPtr> devices(0);
+  mojo::Array<serial::DeviceInfoPtr> devices;
   for (; iter_key.Valid(); ++iter_key) {
     serial::DeviceInfoPtr info(serial::DeviceInfo::New());
     info->path = base::UTF16ToASCII(iter_key.Value());
diff --git a/device/usb/mojo/device_manager_impl.cc b/device/usb/mojo/device_manager_impl.cc
index fdb4d5c..78ecaf9 100644
--- a/device/usb/mojo/device_manager_impl.cc
+++ b/device/usb/mojo/device_manager_impl.cc
@@ -135,7 +135,7 @@ void DeviceManagerImpl::OnGetDevices(EnumerationOptionsPtr options,
     filters = options->filters.To<std::vector<UsbDeviceFilter>>();
 
   std::map<std::string, scoped_refptr<UsbDevice>> device_map;
-  mojo::Array<DeviceInfoPtr> requested_devices(0);
+  mojo::Array<DeviceInfoPtr> requested_devices;
   for (const auto& device : devices) {
     if (filters.empty() || UsbDeviceFilter::MatchesAny(device, filters)) {
       device_map[device->guid()] = device;