Default to LS_INFO logging for release builds.

Increases default loglevel for test targets to LS_INFO, which is a no-op
for debug builds but increases logging on release builds.

This is to present better debug info on buildbots when test runs fail.

BUG=
R=henrikg@webrtc.org, kjellander@webrtc.org, stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1479183002 .

Cr-Commit-Position: refs/heads/master@{#10826}

webrtc/base/unittest_main.cc

@@ -93,6 +93,10 @@ int main(int argc, char** argv) {
   rtc::LogMessage::LogTimestamps();
   if (*FLAG_log != '\0') {
     rtc::LogMessage::ConfigureLogging(FLAG_log);
+  } else if (rtc::LogMessage::GetLogToDebug() > rtc::LS_INFO) {
+    // Default to LS_INFO, even for release builds to provide better test
+    // logging.
+    rtc::LogMessage::LogToDebug(rtc::LS_INFO);
   }
 
   // Initialize SSL which are used by several tests.