update_engine: Update libchrome APIs to r395517

The new libchrome has been ported from Chromium and some APIs have
changed. Make necessary changes at call sites.

Change-Id: I6d4ff48ff16357027a6c865550649eea690c1504
diff --git a/common/cpu_limiter.cc b/common/cpu_limiter.cc
index 67c50b6..1d14764 100644
--- a/common/cpu_limiter.cc
+++ b/common/cpu_limiter.cc
@@ -76,7 +76,7 @@
     return false;
   }
   shares_ = shares;
-  LOG(INFO) << "CPU shares = " << shares_;
+  LOG(INFO) << "CPU shares = " << static_cast<int>(shares_);
   return true;
 }