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

src/views/SkEvent.cpp

Index: src/views/SkEvent.cpp
diff --git a/src/views/SkEvent.cpp b/src/views/SkEvent.cpp
index 5316b49a1d4d5ab283f549261ae8e0f0ca04c4fc..b90d03f3d017eae94f8d9a2a355ab54b61d0ac84 100644
--- a/src/views/SkEvent.cpp
+++ b/src/views/SkEvent.cpp
@@ -298,7 +298,7 @@ void SkEvent::postDelay(SkMSec delay) {
     }
 
     if (delay) {
-        this->postTime(SkTime::GetMSecs() + delay);
+        this->postTime(GetMSecsSinceStartup() + delay);
         return;
     }
 
@@ -404,7 +404,7 @@ SkMSec SkEvent::EnqueueTime(SkEvent* evt, SkMSec time) {
         prev->fNextEvent = evt;
     }
 
-    SkMSec delay = globals.fDelayQHead->fTime - SkTime::GetMSecs();
+    SkMSec delay = globals.fDelayQHead->fTime - GetMSecsSinceStartup();
     if ((int32_t)delay <= 0) {
         delay = 1;
     }
@@ -436,7 +436,7 @@ void SkEvent::ServiceQueueTimer()
     globals.fEventMutex.acquire();
 
     bool        wasEmpty = false;
-    SkMSec      now = SkTime::GetMSecs();
+    SkMSec      now = GetMSecsSinceStartup();
     SkEvent*    evt = globals.fDelayQHead;
 
     while (evt)
@@ -485,6 +485,11 @@ int SkEvent::CountEventsOnQueue() {
     return count;
 }
 
+SkMSec SkEvent::GetMSecsSinceStartup() {
+    static const double kEpoch = SkTime::GetMSecs();
+    return static_cast<SkMSec>(SkTime::GetMSecs() - kEpoch);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkEvent::Init() {}