Cleanup: Pass std::string as const reference from ash/ + minor coding style changes in base/

base/logging.h

Index: base/logging.h
diff --git a/base/logging.h b/base/logging.h
index f91d174b340246341def089373b7b8d0c52d5e39..f49511832bd95f149cc572462e6dd917cf3adb86 100644
--- a/base/logging.h
+++ b/base/logging.h
@@ -806,7 +806,7 @@ class BASE_EXPORT LogMessage {
 
 // A non-macro interface to the log facility; (useful
 // when the logging level is not a compile-time constant).
-inline void LogAtLevel(int const log_level, std::string const &msg) {
+inline void LogAtLevel(int log_level, const std::string& msg) {
   LogMessage(__FILE__, __LINE__, log_level).stream() << msg;
 }