transcoding: drop transcoding request when uid is gone

bug: 184181113
test: transcoding unit tests;
manually testing kill Yelp app during long transcoding,
verify in log that session is cancelled after app kill.

Change-Id: I721c1d4cbf8ae9d6ff328766e4b9fd725f86f8b8
diff --git a/services/mediatranscoding/tests/MediaTranscodingServiceTestHelper.h b/services/mediatranscoding/tests/MediaTranscodingServiceTestHelper.h
index 0d462d1..4727e48 100644
--- a/services/mediatranscoding/tests/MediaTranscodingServiceTestHelper.h
+++ b/services/mediatranscoding/tests/MediaTranscodingServiceTestHelper.h
@@ -524,8 +524,24 @@
         EXPECT_TRUE(mClient3->unregisterClient().isOk());
     }
 
+    const char* prepareOutputFile(const char* path) {
+        deleteFile(path);
+        return path;
+    }
+
     void deleteFile(const char* path) { unlink(path); }
 
+    void dismissKeyguard() {
+        EXPECT_TRUE(ShellHelper::RunCmd("input keyevent KEYCODE_WAKEUP"));
+        EXPECT_TRUE(ShellHelper::RunCmd("wm dismiss-keyguard"));
+    }
+
+    void stopAppPackages() {
+        EXPECT_TRUE(ShellHelper::Stop(kClientPackageA));
+        EXPECT_TRUE(ShellHelper::Stop(kClientPackageB));
+        EXPECT_TRUE(ShellHelper::Stop(kClientPackageC));
+    }
+
     std::shared_ptr<IMediaTranscodingService> mService;
     std::shared_ptr<TestClientCallback> mClient1;
     std::shared_ptr<TestClientCallback> mClient2;