Fix PPAPI time conversion code to handle epoch times.

ppapi/shared_impl/time_conversion.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ppapi/shared_impl/time_conversion.h"
 
 namespace ppapi {
 
 namespace {
 
@@ skipping 12 matching lines @@
   return time_to_ticks_delta_seconds;
 }
 
 }  // namespace
 
 PP_Time TimeToPPTime(base::Time t) {
   return t.ToDoubleT();
 }
 
 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);
 }
 
 PP_TimeTicks TimeTicksToPPTimeTicks(base::TimeTicks t) {
   return static_cast<double>(t.ToInternalValue()) /
       base::Time::kMicrosecondsPerSecond;
 }
 
 PP_TimeTicks EventTimeToPPTimeTicks(double event_time) {
   return event_time + GetTimeToTimeTicksDeltaInSeconds();
 }
 
 double PPTimeTicksToEventTime(PP_TimeTicks t) {
   return t - GetTimeToTimeTicksDeltaInSeconds();
 }
 
 }  // namespace ppapi