Change SkTime::GetMSecs to double; ensure values stored in SkMSec do not overflow.

include/animator/SkAnimator.h

Index: include/animator/SkAnimator.h
diff --git a/include/animator/SkAnimator.h b/include/animator/SkAnimator.h
index 9bb3642ca0b0d119695a4bb90b7e6c3f0fb46c3a..0fe787c5262ccbc75202db30a903c81be16f63b1 100644
--- a/include/animator/SkAnimator.h
+++ b/include/animator/SkAnimator.h
@@ -443,7 +443,8 @@ public:
     };
 
     /** Sets a user class to return the current time to the animator.
-        Optional; if not called, the system clock will be used by calling SkTime::GetMSecs instead.
+        Optional; if not called, the system clock will be used by calling
+        SkEvent::GetMSecsSinceStartup instead.
         @param callBack the time function
     */
     void setTimeline(const Timeline& );