Add logging for slow device events, limit network UI update rate

chromeos/device_event_log.cc

Index: chromeos/device_event_log.cc
diff --git a/chromeos/device_event_log.cc b/chromeos/device_event_log.cc
index 8251e7d579e80e4a8fbe83656e07942f91a44419..5a5acee805f37e53e0f2ccd1b9bd8e1ac889f3f8 100644
--- a/chromeos/device_event_log.cc
+++ b/chromeos/device_event_log.cc
@@ -17,6 +17,9 @@ namespace {
 
 const size_t kDefaultMaxEntries = 4000;
 
+const int kSlowMethodThresholdMs = 10;
+const int kVerySlowMethodThresholdMs = 50;
+
 DeviceEventLogImpl* g_device_event_log = NULL;
 
 }  // namespace
@@ -83,6 +86,23 @@ DeviceEventLogInstance::~DeviceEventLogInstance() {
   device_event_log::AddEntry(file_, line_, type_, level_, stream_.str());
 }
 
+DeviceLogIfSlow::DeviceLogIfSlow(LogType type,
+                                 const char* file,
+                                 const std::string& name)
+    : file_(file), type_(type), name_(name) {
+}
+
+DeviceLogIfSlow::~DeviceLogIfSlow() {
+  if (timer_.Elapsed().InMilliseconds() >= kSlowMethodThresholdMs) {
+    LogLevel level(LOG_LEVEL_DEBUG);
+    if (timer_.Elapsed().InMilliseconds() >= kVerySlowMethodThresholdMs)
+      level = LOG_LEVEL_ERROR;
+    DEVICE_LOG(type_, level) << "@@@ Slow method: " << file_ << ":" << name_
+                             << ": " << timer_.Elapsed().InMilliseconds()
+                             << "ms";
+  }
+}
+
 }  // namespace internal
 
 }  // namespace device_event_log