Add StdioLogger for command-line tools.

Bug: N/A
Test: ran tests
Change-Id: If366a4ea25aea1becdd3e443eba225e9bd52ebba
diff --git a/base/logging.cpp b/base/logging.cpp
index a33da22..978d56d 100644
--- a/base/logging.cpp
+++ b/base/logging.cpp
@@ -212,6 +212,16 @@
           timestamp, getpid(), GetThreadId(), file, line, message);
 }
 
+void StdioLogger(LogId, LogSeverity severity, const char* /*tag*/, const char* /*file*/,
+                 unsigned int /*line*/, const char* message) {
+  if (severity >= WARNING) {
+    fflush(stdout);
+    fprintf(stderr, "%s: %s\n", getprogname(), message);
+  } else {
+    fprintf(stdout, "%s\n", message);
+  }
+}
+
 void DefaultAborter(const char* abort_message) {
 #ifdef __ANDROID__
   android_set_abort_message(abort_message);