Fix black background when locking with fullscreen window:

base/time_mac.cc

Index: base/time_mac.cc
diff --git a/base/time_mac.cc b/base/time_mac.cc
index 883a35ba129a2d76bbf579f26d26d94ad3a55b39..a055cc385e403a1cffb70e4e2011314acbb99490 100644
--- a/base/time_mac.cc
+++ b/base/time_mac.cc
@@ -99,6 +99,8 @@ const int64 Time::kTimeTToMicrosecondsOffset = kWindowsEpochDeltaMicroseconds;
 
 // static
 Time Time::Now() {
+  if (TimeFactory::instance())
+    return TimeFactory::instance()->TimeNow();
   return FromCFAbsoluteTime(CFAbsoluteTimeGetCurrent());
 }
 
@@ -183,6 +185,8 @@ void Time::Explode(bool is_local, Exploded* exploded) const {
 
 // static
 TimeTicks TimeTicks::Now() {
+  if (TimeFactory::instance())
+    return TimeFactory::instance()->TimeTicksNow();
   return TimeTicks(ComputeCurrentTicks());
 }