Reland of [sensors] Ambient light sensor implementation for ChromeOS and Linux.

device/generic_sensor/platform_sensor_provider.cc

Index: device/generic_sensor/platform_sensor_provider.cc
diff --git a/device/generic_sensor/platform_sensor_provider.cc b/device/generic_sensor/platform_sensor_provider.cc
index 56bc08eca0339156224ddced6862099b905614dd..ce6a4feeb5b0bd908dec11e9b767537f4516e386 100644
--- a/device/generic_sensor/platform_sensor_provider.cc
+++ b/device/generic_sensor/platform_sensor_provider.cc
@@ -10,6 +10,8 @@
 #include "device/generic_sensor/platform_sensor_provider_android.h"
 #elif defined(OS_WIN)
 #include "device/generic_sensor/platform_sensor_provider_win.h"
+#elif defined(OS_LINUX)
+#include "device/generic_sensor/platform_sensor_provider_linux.h"
 #endif
 
 namespace {
@@ -36,8 +38,8 @@ PlatformSensorProvider* PlatformSensorProvider::GetInstance() {
   return PlatformSensorProviderAndroid::GetInstance();
 #elif defined(OS_WIN)
   return PlatformSensorProviderWin::GetInstance();
-#else
-  return nullptr;
+#elif defined(OS_LINUX)
+  return PlatformSensorProviderLinux::GetInstance();
 #endif
 }