Fix black background when locking with fullscreen window:

base/time.h

Index: base/time.h
diff --git a/base/time.h b/base/time.h
index 78d7456b68ae273c3bf27e8aaf93cd3742efe02c..09788326895ea64604c62a4e165edcfd541a6aa7 100644
--- a/base/time.h
+++ b/base/time.h
@@ -638,6 +638,20 @@ inline TimeTicks TimeDelta::operator+(TimeTicks t) const {
   return TimeTicks(t.ticks_ + delta_);
 }
 
+// TimeFactory ----------------------------------------------------------------
+
+class BASE_EXPORT TimeFactory {
+ public:
+  virtual Time TimeNow() = 0;
+  virtual TimeTicks TimeTicksNow() = 0;
+  virtual TimeTicks TimeTicksHighResNow() = 0;
+
+  static TimeFactory* instance() { return instance_; }
+
+ protected:
+  static TimeFactory* instance_;
+};
+
 }  // namespace base
 
 #endif  // BASE_TIME_H_