Android tests call exit() when complete.

[ Merge of http://go/wvgerrit/119804 ]

The coverage framework used by Android requires the process to call
exit() for coverage information to be dumped after the tests.

Android unit tests have been adapted to use the a new main module.
The core test_main.cpp used by integration tests has been updated to
call exit().

Bug: 138941105
Test: Linux and Android unittests
Change-Id: Ifffc7b8290c50dffe527738a36547c1d2fb90bd3

libwvdrmengine/cdm/core/test/test_main.cpp

@@ -5,7 +5,7 @@
 // Use in place of the gtest_main in order to initialize the WvCdmTestBase using
 // command line parameters.
 
-#include <stdio.h>
+#include <stdlib.h>
 
 #include "log.h"
 #include "test_base.h"
@@ -13,5 +13,8 @@
 int main(int argc, char** argv) {
   if (!wvcdm::WvCdmTestBase::Initialize(argc, argv)) return 1;
   ::testing::InitGoogleTest(&argc, argv);
-  return RUN_ALL_TESTS();
+  const int status = RUN_ALL_TESTS();
+  LOGD("CDM test complete with status %d", status);
+  exit(status);  // Explicit call to exit() is required for code coverage.
+  return status;
 }