shill: improve logging

- add logging of D-Bus interactions
- convert some error->Populate calls to Error::PopulateAndLog
- slipped in: some whitespace and spelling fixes

BUG=chromium-os:29882
TEST=unit tests

Change-Id: I29cd455cb74cbf467e978a6dc7db3cadac248e43
Reviewed-on: https://gerrit.chromium.org/gerrit/21383
Commit-Ready: mukesh agrawal <quiche@chromium.org>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
diff --git a/dhcpcd_proxy.cc b/dhcpcd_proxy.cc
index 3e291d8..8b9a9fc 100644
--- a/dhcpcd_proxy.cc
+++ b/dhcpcd_proxy.cc
@@ -32,7 +32,7 @@
 }
 
 void DHCPCDListener::Proxy::EventSignal(const DBus::SignalMessage &signal) {
-  SLOG(DHCP, 2) << __func__;
+  SLOG(DBus, 2) << __func__;
   DBus::MessageIter ri = signal.reader();
   unsigned int pid;
   ri >> pid;
@@ -54,7 +54,7 @@
 
 void DHCPCDListener::Proxy::StatusChangedSignal(
     const DBus::SignalMessage &signal) {
-  SLOG(DHCP, 2) << __func__;
+  SLOG(DBus, 2) << __func__;
   DBus::MessageIter ri = signal.reader();
   unsigned int pid;
   ri >> pid;
@@ -76,10 +76,12 @@
 }
 
 void DHCPCDProxy::Rebind(const string &interface) {
+  SLOG(DBus, 2) << __func__;
   proxy_.Rebind(interface);
 }
 
 void DHCPCDProxy::Release(const string &interface) {
+  SLOG(DBus, 2) << __func__;
   proxy_.Release(interface);
 }
 
@@ -98,11 +100,13 @@
     const uint32_t &/*pid*/,
     const std::string &/*reason*/,
     const DHCPConfig::Configuration &/*configuration*/) {
+  SLOG(DBus, 2) << __func__;
   NOTREACHED();
 }
 
 void DHCPCDProxy::Proxy::StatusChanged(const uint32_t &/*pid*/,
                                        const std::string &/*status*/) {
+  SLOG(DBus, 2) << __func__;
   NOTREACHED();
 }