Space trim and other unit tests. General space clean up.

The space unit tests now include checks on space invariants, in
particular relating to footprint and size.
Out-of-date comments have been removed.
This patch adds PrettySize and PrettyDuration methods to make these
strings more human readable.

Change-Id: I6bc05b2db0d0115b97d666b832fce57bcdd2e091
diff --git a/src/timing_logger.h b/src/timing_logger.h
index 78b168b..b8e545e 100644
--- a/src/timing_logger.h
+++ b/src/timing_logger.h
@@ -41,9 +41,9 @@
   void Dump() {
     LOG(INFO) << name_ << ": begin";
     for (size_t i = 1; i < times_.size(); ++i) {
-      LOG(INFO) << name_ << StringPrintf(": %8lld ms, ", NsToMs(times_[i] - times_[i-1])) << labels_[i];
+      LOG(INFO) << name_ << ": " << PrettyDuration(times_[i] - times_[i-1]) << labels_[i];
     }
-    LOG(INFO) << name_ << ": end, " << NsToMs(times_.back() - times_.front()) << " ms";
+    LOG(INFO) << name_ << ": end, " << PrettyDuration(times_.back() - times_.front());
   }
 
  private: