update_engine: Fix all the "using" declaration usage.

This patch removes unused "using" declarations, that is, declarations
included in a .cc file at a global scope such that "using foo::bar"
that later don't use the identifier "bar" at all.

This also unifies the usage of these identifiers in the .cc files
in favor of using the short name defined by the using declaration.
For example, in several cases the .h refer to a type like
"std::string" because using declarations are forbidden in header
files while the .cc includes "using std::string;" with the purpose
of just writting "string" in the .cc file. Very rarely, the full
identifier is used when a local name ocludes it, for example,
StringVectorToGStrv() and StringVectorToString() in utils.cc named
its argument just "vector" need to refer to std::vector with the
full name. This patch renames those arguments instead.

Finally, it also sorts a few lists of using declarations that weren't
in order.

BUG=None
TEST=FEATURES=test emerge-link update_engine

Change-Id: I30f6b9510ecb7e03640f1951c48d5bb106309840
Reviewed-on: https://chromium-review.googlesource.com/226423
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
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_);
 }