Fix ConnectivityManager memory leak

ConnectivityManager have a self reference static instance. This
causes a leak if context is refernce from a static variable. Using
the applicationContext, which will never be freed for the life of the
application, for the sInstance static instance.

Bug: 202978965
Test: atest ConnectivityManagerTest
Change-Id: I87206e1bfbb1f877b5a10f5fdbc25e2f9f11bef4

framework/src/android/net/ConnectivityManager.java

@@ -2589,9 +2589,24 @@ public class ConnectivityManager {
      * {@hide}
      */
     public ConnectivityManager(Context context, IConnectivityManager service) {
+        this(context, service, true /* newStatic */);
+    }
+
+    private ConnectivityManager(Context context, IConnectivityManager service, boolean newStatic) {
         mContext = Objects.requireNonNull(context, "missing context");
         mService = Objects.requireNonNull(service, "missing IConnectivityManager");
-        sInstance = this;
+        // sInstance is accessed without a lock, so it may actually be reassigned several times with
+        // different ConnectivityManager, but that's still OK considering its usage.
+        if (sInstance == null && newStatic) {
+            final Context appContext = mContext.getApplicationContext();
+            // Don't create static ConnectivityManager instance again to prevent infinite loop.
+            // If the application context is null, we're either in the system process or
+            // it's the application context very early in app initialization. In both these
+            // cases, the passed-in Context will not be freed, so it's safe to pass it to the
+            // service. http://b/27532714 .
+            sInstance = new ConnectivityManager(appContext != null ? appContext : context, service,
+                    false /* newStatic */);
+        }
     }
 
     /** {@hide} */

tests/unit/java/android/net/ConnectivityManagerTest.java

@@ -41,6 +41,7 @@ import static com.android.testutils.MiscAsserts.assertThrows;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.anyBoolean;
@@ -506,8 +507,7 @@ public class ConnectivityManagerTest {
             Thread.sleep(waitIntervalMs);
         }
 
-        // TODO: fix memory leak then assertNull here.
-        assertNotNull("Couldn't find the Context leak in ConnectivityManager after " + attempts
-                + " attempts", ref.get());
+        assertNull("ConnectivityManager weak reference still not null after " + attempts
+                    + " attempts", ref.get());
     }
 }