Reboot test: Initialize fake clock

[ Merge of http://go/wvgerrit/143630 ]

When we run a test with the fake clock, the clock had been initialized
to the current time, or to 0. This causes a problem for reboot tests
because the clock might go backwards over the reboot. With this
change, we monitor the clock at the end of one reboot pass and
initialize the clock for the next pass based on the previous value.

Bug: 26163469
Test: GtsMediaTestCases on sunfish
Change-Id: Ibd0024f963634382af70553fced38da6e1d857d2

libwvdrmengine/cdm/util/test/test_sleep.cpp

@@ -58,6 +58,21 @@ void TestSleep::SyncFakeClock() {
   Sleep(0);
 }
 
+void TestSleep::SetFakeClock(int64_t time_seconds) {
+  if (real_sleep_) {
+    LOGE("SetFakeClock when using a real clock. Expect other failures.");
+  }
+  // Delta could be positive or negative. If the fake clock had been initialized
+  // by the current time on a real clock, and then the command line
+  // re-initializes it to 0, then delta is negative.
+  int64_t delta = time_seconds - Clock().GetCurrentTime();
+  if (callback_ != nullptr) {
+    callback_->ElapseTime(delta * 1000);
+  } else {
+    LOGE("Setting fake clock with no callback. This won't work.");
+  }
+}
+
 bool TestSleep::RollbackSystemTime(int seconds) {
   if (real_sleep_) {
 #ifdef _WIN32