[fuchsia] Clean up logging to the Fuchsia logger

This improves readability for the code responsible for logging to the
Fuchsia logger service. This also skips instantiating a variable if no
logger is available.

Bug: 1188820
Change-Id: I39d22a2f8a934e115af7ad95728432a60bfc2dab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2819363
Reviewed-by: David Dorwin <ddorwin@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#873045}

base/logging.cc

@@ -346,6 +346,30 @@ void CloseLogFileUnlocked() {
     g_logging_destination &= ~LOG_TO_FILE;
 }
 
+#if defined(OS_FUCHSIA)
+
+inline fx_log_severity_t LogSeverityToFuchsiaLogSeverity(LogSeverity severity) {
+  switch (severity) {
+    case LOGGING_INFO:
+      return FX_LOG_INFO;
+    case LOGGING_WARNING:
+      return FX_LOG_WARNING;
+    case LOGGING_ERROR:
+      return FX_LOG_ERROR;
+    case LOGGING_FATAL:
+      // Don't use FX_LOG_FATAL, otherwise fx_logger_log() will abort().
+      return FX_LOG_ERROR;
+  }
+  if (severity > -3) {
+    // LOGGING_VERBOSE levels 1 and 2.
+    return FX_LOG_DEBUG;
+  }
+  // LOGGING_VERBOSE levels 3 and higher, or incorrect levels.
+  return FX_LOG_TRACE;
+}
+
+#endif  // defined (OS_FUCHSIA)
+
 }  // namespace
 
 #if defined(DCHECK_IS_CONFIGURABLE)
@@ -401,7 +425,7 @@ bool BaseInitLoggingImpl(const LoggingSettings& settings) {
     const char* log_tag_data = log_tag.data();
 
     fx_logger_config_t config = {
-        .min_severity = g_vlog_info ? FX_LOG_DEBUG : FX_LOG_INFO,
+        .min_severity = g_vlog_info ? FX_LOG_TRACE : FX_LOG_INFO,
         .console_fd = -1,
         .tags = &log_tag_data,
         .num_tags = 1,
@@ -778,35 +802,14 @@ LogMessage::~LogMessage() {
     __android_log_write(priority, kAndroidLogTag, str_newline.c_str());
 #endif
 #elif defined(OS_FUCHSIA)
-    fx_log_severity_t severity = FX_LOG_INFO;
-    switch (severity_) {
-      case LOGGING_INFO:
-        severity = FX_LOG_INFO;
-        break;
-      case LOGGING_WARNING:
-        severity = FX_LOG_WARNING;
-        break;
-      case LOGGING_ERROR:
-        severity = FX_LOG_ERROR;
-        break;
-      case LOGGING_FATAL:
-        // Don't use FX_LOG_FATAL, otherwise fx_logger_log() will abort().
-        severity = FX_LOG_ERROR;
-        break;
-    }
-    // TODO(https://crbug.com/1188820): Integrate verbose levels with the switch
-    // statement.
-    if (severity_ <= LOGGING_VERBOSE) {
-      severity = FX_LOG_DEBUG;
-    }
-
     fx_logger_t* logger = fx_log_get_logger();
     if (logger) {
       // Temporarily remove the trailing newline from |str_newline|'s C-string
       // representation, since fx_logger will add a newline of its own.
       str_newline.pop_back();
-      fx_logger_log_with_source(logger, severity, nullptr, file_, line_,
+      fx_logger_log_with_source(
-                                str_newline.c_str() + message_start_);
+          logger, LogSeverityToFuchsiaLogSeverity(severity_), nullptr, file_,
+          line_, str_newline.c_str() + message_start_);
       str_newline.push_back('\n');
     }
 #endif  // OS_FUCHSIA