dbus: Filter signal by the sender we are interested in only.

This adds sender='<name>' filter as the match rule for subscribing to
signal in ObjectProxy. This is needed to reduce the unnecessary polluted
log of rejecting some signals. The manual sender verification is still
needed because as mentioned in
https://bugs.chromium.org/p/chromium/issues/detail?id=507206#c14
service_name_ might be empty and sender='' means to not filter by sender
at all.

BUG=chromium:812468
TEST=Tested on device and checked that communications to D-Bus services
(e.g. power, bluetooth) don't break

Change-Id: I0ef4e03b5d9d8aa4412ef97286b971c30f458e99
Reviewed-on: https://chromium-review.googlesource.com/958324Reviewed-by: Satoru Takabayashi <satorux@chromium.org>
Commit-Queue: Sonny Sasaka <sonnysasaka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542567}

dbus/object_proxy.cc

@@ -463,9 +463,9 @@ bool ObjectProxy::ConnectToSignalInternal(const std::string& interface_name,
       GetAbsoluteMemberName(interface_name, signal_name);
 
   // Add a match rule so the signal goes through HandleMessage().
-  const std::string match_rule =
-      base::StringPrintf("type='signal', interface='%s', path='%s'",
-                         interface_name.c_str(),
+  const std::string match_rule = base::StringPrintf(
+      "type='signal', sender='%s', interface='%s', path='%s'",
+      service_name_.c_str(), interface_name.c_str(),
       object_path_.value().c_str());
   return AddMatchRuleWithCallback(match_rule,
                                   absolute_signal_name,