diff --git a/update_manager/boxed_value.cc b/update_manager/boxed_value.cc
index 773431c..2307f8d 100644
--- a/update_manager/boxed_value.cc
+++ b/update_manager/boxed_value.cc
@@ -78,7 +78,7 @@
   return chromeos_update_engine::utils::FormatTimeDelta(*val);
 }
 
-static std::string ConnectionTypeToString(ConnectionType type) {
+static string ConnectionTypeToString(ConnectionType type) {
   switch (type) {
     case ConnectionType::kEthernet:
       return "Ethernet";
diff --git a/update_manager/chromeos_policy.cc b/update_manager/chromeos_policy.cc
index 19f9dc8..86a2dc4 100644
--- a/update_manager/chromeos_policy.cc
+++ b/update_manager/chromeos_policy.cc
@@ -516,7 +516,7 @@
       ec->GetValue(updater_provider->var_updater_started_time());
   POLICY_CHECK_VALUE_AND_FAIL(updater_started_time, error);
 
-  const base::Time* last_checked_time =
+  const Time* last_checked_time =
       ec->GetValue(updater_provider->var_last_checked_time());
 
   const uint64_t* seed = ec->GetValue(state->random_provider()->var_seed());
@@ -587,7 +587,7 @@
 }
 
 EvalStatus ChromeOSPolicy::UpdateBackoffAndDownloadUrl(
-    EvaluationContext* ec, State* state, std::string* error,
+    EvaluationContext* ec, State* state, string* error,
     UpdateBackoffAndDownloadUrlResult* result,
     const UpdateState& update_state) const {
   // Sanity checks.
@@ -755,10 +755,10 @@
     const uint64_t* seed = ec->GetValue(state->random_provider()->var_seed());
     POLICY_CHECK_VALUE_AND_FAIL(seed, error);
     PRNG prng(*seed);
-    int exp = std::min(update_state.num_failures,
+    int exp = min(update_state.num_failures,
                        static_cast<int>(sizeof(int)) * 8 - 2);
     TimeDelta backoff_interval = TimeDelta::FromDays(
-        std::min(1 << exp, kAttemptBackoffMaxIntervalInDays));
+        min(1 << exp, kAttemptBackoffMaxIntervalInDays));
     TimeDelta backoff_fuzz = TimeDelta::FromHours(kAttemptBackoffFuzzInHours);
     TimeDelta wait_period = FuzzedInterval(&prng, backoff_interval.InSeconds(),
                                            backoff_fuzz.InSeconds());
diff --git a/update_manager/chromeos_policy_unittest.cc b/update_manager/chromeos_policy_unittest.cc
index 10e6324..b99074c 100644
--- a/update_manager/chromeos_policy_unittest.cc
+++ b/update_manager/chromeos_policy_unittest.cc
@@ -21,7 +21,6 @@
 using base::TimeDelta;
 using chromeos_update_engine::ErrorCode;
 using chromeos_update_engine::FakeClock;
-using std::make_tuple;
 using std::set;
 using std::string;
 using std::tuple;
@@ -1019,7 +1018,8 @@
   update_state.p2p_num_attempts = 1;
   update_state.p2p_first_attempted =
       fake_clock_.GetWallclockTime() -
-      TimeDelta::FromSeconds(ChromeOSPolicy::kMaxP2PAttemptsPeriodInSeconds + 1);
+      TimeDelta::FromSeconds(
+          ChromeOSPolicy::kMaxP2PAttemptsPeriodInSeconds + 1);
   UpdateDownloadParams result;
   ExpectPolicyStatus(EvalStatus::kSucceeded, &Policy::UpdateCanStart, &result,
                      update_state);
diff --git a/update_manager/evaluation_context.cc b/update_manager/evaluation_context.cc
index 9ab6771..3584ac8 100644
--- a/update_manager/evaluation_context.cc
+++ b/update_manager/evaluation_context.cc
@@ -28,8 +28,8 @@
 // Returns whether |curr_time| surpassed |ref_time|; if not, also checks whether
 // |ref_time| is sooner than the current value of |*reeval_time|, in which case
 // the latter is updated to the former.
-bool IsTimeGreaterThanHelper(base::Time ref_time, base::Time curr_time,
-                             base::Time* reeval_time) {
+bool IsTimeGreaterThanHelper(Time ref_time, Time curr_time,
+                             Time* reeval_time) {
   if (curr_time > ref_time)
     return true;
   // Remember the nearest reference we've checked against in this evaluation.
@@ -40,7 +40,7 @@
 
 // If |expires| never happens (maximal value), returns the maximal interval;
 // otherwise, returns the difference between |expires| and |curr|.
-TimeDelta GetTimeout(base::Time curr, base::Time expires) {
+TimeDelta GetTimeout(Time curr, Time expires) {
   if (expires.is_max())
     return TimeDelta::Max();
   return expires - curr;
@@ -114,12 +114,12 @@
     callback->Run();
 }
 
-bool EvaluationContext::IsWallclockTimeGreaterThan(base::Time timestamp) {
+bool EvaluationContext::IsWallclockTimeGreaterThan(Time timestamp) {
   return IsTimeGreaterThanHelper(timestamp, evaluation_start_wallclock_,
                                  &reevaluation_time_wallclock_);
 }
 
-bool EvaluationContext::IsMonotonicTimeGreaterThan(base::Time timestamp) {
+bool EvaluationContext::IsMonotonicTimeGreaterThan(Time timestamp) {
   return IsTimeGreaterThanHelper(timestamp, evaluation_start_monotonic_,
                                  &reevaluation_time_monotonic_);
 }
diff --git a/update_manager/evaluation_context_unittest.cc b/update_manager/evaluation_context_unittest.cc
index 014d10c..19e3419 100644
--- a/update_manager/evaluation_context_unittest.cc
+++ b/update_manager/evaluation_context_unittest.cc
@@ -101,7 +101,7 @@
     EXPECT_TRUE(fake_poll_var_.observer_list_.empty());
   }
 
-  base::TimeDelta default_timeout_ = base::TimeDelta::FromSeconds(5);
+  TimeDelta default_timeout_ = TimeDelta::FromSeconds(5);
 
   FakeClock fake_clock_;
   scoped_refptr<EvaluationContext> eval_ctx_;
@@ -344,7 +344,7 @@
 }
 
 TEST_F(UmEvaluationContextTest, ResetEvaluationResetsTimesWallclock) {
-  base::Time cur_time = fake_clock_.GetWallclockTime();
+  Time cur_time = fake_clock_.GetWallclockTime();
   // Advance the time on the clock but don't call ResetEvaluation yet.
   fake_clock_.SetWallclockTime(cur_time + TimeDelta::FromSeconds(4));
 
@@ -365,7 +365,7 @@
 }
 
 TEST_F(UmEvaluationContextTest, ResetEvaluationResetsTimesMonotonic) {
-  base::Time cur_time = fake_clock_.GetMonotonicTime();
+  Time cur_time = fake_clock_.GetMonotonicTime();
   // Advance the time on the clock but don't call ResetEvaluation yet.
   fake_clock_.SetMonotonicTime(cur_time + TimeDelta::FromSeconds(4));
 
diff --git a/update_manager/generic_variables_unittest.cc b/update_manager/generic_variables_unittest.cc
index f0ea60c..784ac4a 100644
--- a/update_manager/generic_variables_unittest.cc
+++ b/update_manager/generic_variables_unittest.cc
@@ -12,7 +12,6 @@
 #include "update_engine/test_utils.h"
 #include "update_engine/update_manager/umtest_utils.h"
 
-using base::TimeDelta;
 using chromeos_update_engine::RunGMainLoopMaxIterations;
 using std::unique_ptr;
 
diff --git a/update_manager/real_config_provider.cc b/update_manager/real_config_provider.cc
index d986b10..ac334c4 100644
--- a/update_manager/real_config_provider.cc
+++ b/update_manager/real_config_provider.cc
@@ -13,7 +13,6 @@
 #include "update_engine/utils.h"
 
 using chromeos::KeyValueStore;
-using std::string;
 
 namespace {
 
diff --git a/update_manager/real_device_policy_provider.cc b/update_manager/real_device_policy_provider.cc
index 9a68956..f74a7be 100644
--- a/update_manager/real_device_policy_provider.cc
+++ b/update_manager/real_device_policy_provider.cc
@@ -51,7 +51,7 @@
 template<typename T>
 void RealDevicePolicyProvider::UpdateVariable(
     AsyncCopyVariable<T>* var,
-    bool (policy::DevicePolicy::*getter_method)(T*) const) {
+    bool (DevicePolicy::*getter_method)(T*) const) {
   T new_value;
   if (policy_provider_->device_policy_is_loaded() &&
       (policy_provider_->GetDevicePolicy().*getter_method)(&new_value)) {
@@ -95,7 +95,7 @@
 }
 
 bool RealDevicePolicyProvider::ConvertScatterFactor(
-    base::TimeDelta* scatter_factor) const {
+    TimeDelta* scatter_factor) const {
   int64_t scatter_factor_in_seconds;
   if (!policy_provider_->GetDevicePolicy().GetScatterFactorInSeconds(
       &scatter_factor_in_seconds)) {
@@ -106,7 +106,7 @@
                  << scatter_factor_in_seconds;
     return false;
   }
-  *scatter_factor = base::TimeDelta::FromSeconds(scatter_factor_in_seconds);
+  *scatter_factor = TimeDelta::FromSeconds(scatter_factor_in_seconds);
   return true;
 }
 
diff --git a/update_manager/real_device_policy_provider_unittest.cc b/update_manager/real_device_policy_provider_unittest.cc
index 52b036b..627027e 100644
--- a/update_manager/real_device_policy_provider_unittest.cc
+++ b/update_manager/real_device_policy_provider_unittest.cc
@@ -18,7 +18,6 @@
 using std::set;
 using std::string;
 using std::unique_ptr;
-using testing::AtLeast;
 using testing::DoAll;
 using testing::Mock;
 using testing::Return;
@@ -138,7 +137,7 @@
       .WillOnce(DoAll(SetArgumentPointee<0>(1234), Return(true)));
   EXPECT_TRUE(provider_->Init());
 
-  UmTestUtils::ExpectVariableHasValue(base::TimeDelta::FromSeconds(1234),
+  UmTestUtils::ExpectVariableHasValue(TimeDelta::FromSeconds(1234),
                                       provider_->var_scatter_factor());
 }
 
diff --git a/update_manager/real_random_provider_unittest.cc b/update_manager/real_random_provider_unittest.cc
index d7b2d98..d7dfeb2 100644
--- a/update_manager/real_random_provider_unittest.cc
+++ b/update_manager/real_random_provider_unittest.cc
@@ -9,7 +9,6 @@
 #include "update_engine/update_manager/real_random_provider.h"
 #include "update_engine/update_manager/umtest_utils.h"
 
-using base::TimeDelta;
 using std::unique_ptr;
 
 namespace chromeos_update_manager {
diff --git a/update_manager/real_shill_provider_unittest.cc b/update_manager/real_shill_provider_unittest.cc
index 7c64d81..7859501 100644
--- a/update_manager/real_shill_provider_unittest.cc
+++ b/update_manager/real_shill_provider_unittest.cc
@@ -26,7 +26,6 @@
 using std::unique_ptr;
 using testing::Eq;
 using testing::Mock;
-using testing::NiceMock;
 using testing::Return;
 using testing::SaveArg;
 using testing::SetArgPointee;
diff --git a/update_manager/real_system_provider.cc b/update_manager/real_system_provider.cc
index 8d5f4f4..1410106 100644
--- a/update_manager/real_system_provider.cc
+++ b/update_manager/real_system_provider.cc
@@ -20,11 +20,7 @@
 #include "update_engine/update_manager/generic_variables.h"
 #include "update_engine/utils.h"
 
-using base::StringPrintf;
-using base::Time;
-using base::TimeDelta;
 using std::string;
-using std::vector;
 
 namespace chromeos_update_manager {
 
diff --git a/update_manager/real_time_provider.cc b/update_manager/real_time_provider.cc
index e9ac3c2..dab9829 100644
--- a/update_manager/real_time_provider.cc
+++ b/update_manager/real_time_provider.cc
@@ -26,7 +26,7 @@
       : Variable<Time>(name, TimeDelta::FromHours(1)), clock_(clock) {}
 
  protected:
-  virtual const Time* GetValue(base::TimeDelta /* timeout */,
+  virtual const Time* GetValue(TimeDelta /* timeout */,
                                string* /* errmsg */) {
     Time::Exploded now_exp;
     clock_->GetWallclockTime().LocalExplode(&now_exp);
@@ -49,7 +49,7 @@
       : Variable<int>(name, TimeDelta::FromMinutes(5)), clock_(clock) {}
 
  protected:
-  virtual const int* GetValue(base::TimeDelta /* timeout */,
+  virtual const int* GetValue(TimeDelta /* timeout */,
                               string* /* errmsg */) {
     Time::Exploded exploded;
     clock_->GetWallclockTime().LocalExplode(&exploded);
diff --git a/update_manager/real_time_provider_unittest.cc b/update_manager/real_time_provider_unittest.cc
index da69e49..3532ff3 100644
--- a/update_manager/real_time_provider_unittest.cc
+++ b/update_manager/real_time_provider_unittest.cc
@@ -13,7 +13,6 @@
 #include "update_engine/update_manager/umtest_utils.h"
 
 using base::Time;
-using base::TimeDelta;
 using chromeos_update_engine::FakeClock;
 using std::unique_ptr;
 
diff --git a/update_manager/real_updater_provider_unittest.cc b/update_manager/real_updater_provider_unittest.cc
index eeee245..1477187 100644
--- a/update_manager/real_updater_provider_unittest.cc
+++ b/update_manager/real_updater_provider_unittest.cc
@@ -22,7 +22,6 @@
 using base::TimeDelta;
 using chromeos_update_engine::FakeClock;
 using chromeos_update_engine::FakeSystemState;
-using chromeos_update_engine::MockUpdateAttempter;
 using chromeos_update_engine::OmahaRequestParams;
 using chromeos_update_engine::PrefsMock;
 using std::string;
diff --git a/update_manager/update_manager_unittest.cc b/update_manager/update_manager_unittest.cc
index a9e4b22..42edc40 100644
--- a/update_manager/update_manager_unittest.cc
+++ b/update_manager/update_manager_unittest.cc
@@ -35,9 +35,6 @@
 using std::tuple;
 using std::unique_ptr;
 using std::vector;
-using testing::Return;
-using testing::StrictMock;
-using testing::_;
 
 namespace {
 
@@ -89,7 +86,7 @@
   }
 
  protected:
-  std::string PolicyName() const override { return "FailingPolicy"; }
+  string PolicyName() const override { return "FailingPolicy"; }
 
  private:
   int* num_called_p_;
@@ -104,7 +101,7 @@
   }
 
  protected:
-  std::string PolicyName() const override { return "LazyPolicy"; }
+  string PolicyName() const override { return "LazyPolicy"; }
 };
 
 // A policy that sleeps for a predetermined amount of time, then checks for a
@@ -137,7 +134,7 @@
   }
 
  protected:
-  std::string PolicyName() const override { return "DelayPolicy"; }
+  string PolicyName() const override { return "DelayPolicy"; }
 
  private:
   int sleep_secs_;