chromeos: Add CHROMEOS_EXPORT to CPUTemperatureReader

chromeos/system/cpu_temperature_reader.h

Index: chromeos/system/cpu_temperature_reader.h
diff --git a/chromeos/system/cpu_temperature_reader.h b/chromeos/system/cpu_temperature_reader.h
index 45c77ed5e4259f468f1ba5377f1d74aeca825f9d..d32672525f8f7d6ea06069d8f459de0efd6546f6 100644
--- a/chromeos/system/cpu_temperature_reader.h
+++ b/chromeos/system/cpu_temperature_reader.h
@@ -11,12 +11,13 @@
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
+#include "chromeos/chromeos_export.h"
 
 namespace chromeos {
 namespace system {
 
 // Used to read CPU temperature info from sysfs hwmon.
-class CPUTemperatureReader {
+class CHROMEOS_EXPORT CPUTemperatureReader {
  public:
   // Contains info from a CPU temperature sensor.
   struct CPUTemperatureInfo {