update_engine: Replace NULL with nullptr

Replaced the usage of NULL with nullptr. This also makes it possible to
use standard gtest macros to compare pointers in Update Manager's unit tests.
So, there is no need in custom UMTEST_... macros which are replaced with the
gtest macros (see change in update_engine/update_manager/umtest_utils.h):

UMTEST_ASSERT_NULL(p)      => ASSERT_EQ(nullptr, p)
UMTEST_ASSERT_NOT_NULL(p)  => ASSERT_NE(nullptr, p)
UMTEST_EXPECT_NULL(p)      => EXPECT_EQ(nullptr, p)
UMTEST_EXPECT_NOT_NULL(p)  => EXPECT_NE(nullptr, p)

BUG=None
TEST=FEATURES=test emerge-link update_engine
     USE="clang asan" FEATURES=test emerge-link update_engine

Change-Id: I77a42a1e9ce992bb2f9f263db5cf75fe6110a4ec
Reviewed-on: https://chromium-review.googlesource.com/215136
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/update_engine_client.cc b/update_engine_client.cc
index eb092b5..37d52d6 100644
--- a/update_engine_client.cc
+++ b/update_engine_client.cc
@@ -71,13 +71,13 @@
 
 bool GetProxy(DBusGProxy** out_proxy) {
   DBusGConnection* bus;
-  DBusGProxy* proxy = NULL;
-  GError* error = NULL;
+  DBusGProxy* proxy = nullptr;
+  GError* error = nullptr;
   const int kTries = 4;
   const int kRetrySeconds = 10;
 
   bus = dbus_g_bus_get(DBUS_BUS_SYSTEM, &error);
-  if (bus == NULL) {
+  if (bus == nullptr) {
     LOG(ERROR) << "Failed to get bus: " << GetAndFreeGError(&error);
     exit(1);
   }
@@ -96,7 +96,7 @@
                             << kUpdateEngineServiceName << ": "
                             << GetAndFreeGError(&error);
   }
-  if (proxy == NULL) {
+  if (proxy == nullptr) {
     LOG(ERROR) << "Giving up -- unable to get dbus proxy for "
                << kUpdateEngineServiceName;
     exit(1);
@@ -122,7 +122,7 @@
 
 bool ResetStatus() {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -131,18 +131,18 @@
 }
 
 
-// If |op| is non-NULL, sets it to the current operation string or an
+// If |op| is non-null, sets it to the current operation string or an
 // empty string if unable to obtain the current status.
 bool GetStatus(string* op) {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
   gint64 last_checked_time = 0;
   gdouble progress = 0.0;
-  char* current_op = NULL;
-  char* new_version = NULL;
+  char* current_op = nullptr;
+  char* new_version = nullptr;
   gint64 new_size = 0;
 
   gboolean rc = update_engine_client_get_status(proxy,
@@ -194,19 +194,19 @@
                           G_TYPE_STRING,
                           G_TYPE_INT64,
                           G_TYPE_INVALID);
-  GMainLoop* loop = g_main_loop_new(NULL, TRUE);
+  GMainLoop* loop = g_main_loop_new(nullptr, TRUE);
   dbus_g_proxy_connect_signal(proxy,
                               kStatusUpdate,
                               G_CALLBACK(StatusUpdateSignalHandler),
-                              NULL,
-                              NULL);
+                              nullptr,
+                              nullptr);
   g_main_loop_run(loop);
   g_main_loop_unref(loop);
 }
 
 bool Rollback(bool rollback) {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -220,7 +220,7 @@
 
 std::string GetRollbackPartition() {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -254,7 +254,7 @@
 
 bool CheckForUpdates(const string& app_version, const string& omaha_url) {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -273,7 +273,7 @@
 
 bool RebootIfNeeded() {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -288,7 +288,7 @@
 
 void SetTargetChannel(const string& target_channel, bool allow_powerwash) {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -303,11 +303,11 @@
 
 string GetChannel(bool get_current_channel) {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
-  char* channel = NULL;
+  char* channel = nullptr;
   gboolean rc = update_engine_client_get_channel(proxy,
                                                  get_current_channel,
                                                  &channel,
@@ -321,7 +321,7 @@
 
 void SetUpdateOverCellularPermission(gboolean allowed) {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -335,7 +335,7 @@
 
 bool GetUpdateOverCellularPermission() {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -351,7 +351,7 @@
 
 void SetP2PUpdatePermission(gboolean enabled) {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -365,7 +365,7 @@
 
 bool GetP2PUpdatePermission() {
   DBusGProxy* proxy;
-  GError* error = NULL;
+  GError* error = nullptr;
 
   CHECK(GetProxy(&proxy));
 
@@ -396,8 +396,8 @@
 // a signal watch, actively poll the daemon just in case it stops
 // sending notifications.
 void CompleteUpdate() {
-  GMainLoop* loop = g_main_loop_new(NULL, TRUE);
-  g_timeout_add_seconds(5, CompleteUpdateSource, NULL);
+  GMainLoop* loop = g_main_loop_new(nullptr, TRUE);
+  g_timeout_add_seconds(5, CompleteUpdateSource, nullptr);
   g_main_loop_run(loop);
   g_main_loop_unref(loop);
 }
@@ -663,7 +663,7 @@
 
   if (FLAGS_status) {
     LOG(INFO) << "Querying Update Engine status...";
-    if (!GetStatus(NULL)) {
+    if (!GetStatus(nullptr)) {
       LOG(ERROR) << "GetStatus failed.";
       return 1;
     }