update_engine: Replace scoped_refptr with shared_ptr in update_manager

It seems like scoped_refptr was a substitute for shared_ptr before
chromium was on C++11:
https://www.chromium.org/developers/smart-pointer-guidelines

But that is not the case anymore as we are already on C++14. So just
replace it in update_manager with shared_ptr.

There is still another use case of it for keeping dbus connections but
that can't easily be changed because brillo::DBusConnection is still
using scoped_refptr.

BUG=chromium:994048
TEST=FEATURES=test emerge update_engine

Change-Id: I1fab0408399d678d2851731aea40fc02be459295
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/1755262
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
diff --git a/update_manager/evaluation_context_unittest.cc b/update_manager/evaluation_context_unittest.cc
index 151b0b5..a50defd 100644
--- a/update_manager/evaluation_context_unittest.cc
+++ b/update_manager/evaluation_context_unittest.cc
@@ -39,6 +39,7 @@
 using brillo::MessageLoopRunMaxIterations;
 using brillo::MessageLoopRunUntil;
 using chromeos_update_engine::FakeClock;
+using std::shared_ptr;
 using std::string;
 using std::unique_ptr;
 using testing::_;
@@ -59,14 +60,14 @@
 }
 
 template <typename T>
-void ReadVar(scoped_refptr<EvaluationContext> ec, Variable<T>* var) {
+void ReadVar(shared_ptr<EvaluationContext> ec, Variable<T>* var) {
   ec->GetValue(var);
 }
 
 // Runs |evaluation|; if the value pointed by |count_p| is greater than zero,
 // decrement it and schedule a reevaluation; otherwise, writes true to |done_p|.
 void EvaluateRepeatedly(Closure evaluation,
-                        scoped_refptr<EvaluationContext> ec,
+                        shared_ptr<EvaluationContext> ec,
                         int* count_p,
                         bool* done_p) {
   evaluation.Run();
@@ -92,11 +93,11 @@
     fake_clock_.SetMonotonicTime(Time::FromTimeT(1240428300));
     // Mar 2, 2006 1:23:45 UTC.
     fake_clock_.SetWallclockTime(Time::FromTimeT(1141262625));
-    eval_ctx_ = new EvaluationContext(
+    eval_ctx_.reset(new EvaluationContext(
         &fake_clock_,
         default_timeout_,
         default_timeout_,
-        unique_ptr<base::Callback<void(EvaluationContext*)>>(nullptr));
+        unique_ptr<base::Callback<void(EvaluationContext*)>>(nullptr)));
   }
 
   void TearDown() override {
@@ -126,7 +127,7 @@
 
   brillo::FakeMessageLoop loop_{nullptr};
   FakeClock fake_clock_;
-  scoped_refptr<EvaluationContext> eval_ctx_;
+  shared_ptr<EvaluationContext> eval_ctx_;
 
   // FakeVariables used for testing the EvaluationContext. These are required
   // here to prevent them from going away *before* the EvaluationContext under