Fix PPAPI time conversion code to handle epoch times.

ppapi/shared_impl/time_conversion.cc

Index: ppapi/shared_impl/time_conversion.cc
diff --git a/ppapi/shared_impl/time_conversion.cc b/ppapi/shared_impl/time_conversion.cc
index 53d7b99de03b02726c4a28a8c7e2b5de82ff14fd..07ca6f73a2c5269661bf6be5f6acae13dd3ee5ea 100644
--- a/ppapi/shared_impl/time_conversion.cc
+++ b/ppapi/shared_impl/time_conversion.cc
@@ -30,6 +30,12 @@ PP_Time TimeToPPTime(base::Time t) {
 }
 
 base::Time PPTimeToTime(PP_Time t) {
+  // The time code handles exact "0" values as special, and produces
+  // a "null" Time object. But calling code would expect t==0 to represent the
+  // epoch (according to the description of PP_Time). Hence we just return the
+  // epoch in this case.
+  if (t == 0.0)
+    return base::Time::UnixEpoch();
   return base::Time::FromDoubleT(t);
 }