Remove logging::LogAtLevel and rewrite its sole caller.

base/logging.h

Index: base/logging.h
diff --git a/base/logging.h b/base/logging.h
index 300c9b52694b09068bc051a38494d382cb7350d7..fe00ca1a86f793b9c60e0aa1808931fd7ec7d6a7 100644
--- a/base/logging.h
+++ b/base/logging.h
@@ -807,12 +807,6 @@ class BASE_EXPORT LogMessage {
   DISALLOW_COPY_AND_ASSIGN(LogMessage);
 };
 
-// A non-macro interface to the log facility; (useful
-// when the logging level is not a compile-time constant).
-inline void LogAtLevel(int log_level, const std::string& msg) {
-  LogMessage(__FILE__, __LINE__, log_level).stream() << msg;
-}
-
 // This class is used to explicitly ignore values in the conditional
 // logging macros.  This avoids compiler warnings like "value computed
 // is not used" and "statement has no effect".