Ref count Timer implementation

[ Merge of http://go/wvgerrit/78763 ]

The android timer instance is held by a regular pointer rather
than reference counted as all classes that derive from RefBase
should be. This could result in a double deallocation, if the
timer is ever passed to a strong pointer.

Bug: 79364026
Test: WV unit/integration tests. GtsMediaTestCases. Play movies
      playback tests.

Change-Id: I01f622bc045e1012f2240b3775a6d121f9415463

libwvdrmengine/cdm/src/timer.cpp

@@ -81,9 +81,6 @@ Timer::Timer() : impl_(new Timer::Impl()) {
 Timer::~Timer() {
   if (IsRunning())
     Stop();
-
-  delete impl_;
-  impl_ = NULL;
 }
 
 bool Timer::Start(TimerHandler *handler, uint32_t time_in_secs) {