Partial cherry-pick to remove IoUtils#deleteContents usage in FrameworksNetTests

It's a partial cherry-pick of https://r.android.com/1731232

Bug: 154796679
eest: atest ConnectivityCoverageTests
Merged-In: I5366e1cc9cd6ddb41f24718246381cc2b1cc1383
Change-Id: I23565c4144e665130585a86ce66cee6c2da07b60
diff --git a/tests/unit/Android.bp b/tests/unit/Android.bp
index beae0cf..909a192 100644
--- a/tests/unit/Android.bp
+++ b/tests/unit/Android.bp
@@ -65,6 +65,7 @@
     static_libs: [
         "androidx.test.rules",
         "bouncycastle-repackaged-unbundled",
+        "core-tests-support",
         "FrameworksNetCommonTests",
         "frameworks-base-testutils",
         "frameworks-net-integration-testutils",
diff --git a/tests/unit/java/com/android/server/net/NetworkStatsFactoryTest.java b/tests/unit/java/com/android/server/net/NetworkStatsFactoryTest.java
index f3ae9b0..40d4446 100644
--- a/tests/unit/java/com/android/server/net/NetworkStatsFactoryTest.java
+++ b/tests/unit/java/com/android/server/net/NetworkStatsFactoryTest.java
@@ -46,6 +46,7 @@
 
 import libcore.io.IoUtils;
 import libcore.io.Streams;
+import libcore.testing.io.TestIoUtils;
 
 import org.junit.After;
 import org.junit.Before;
@@ -69,10 +70,7 @@
 
     @Before
     public void setUp() throws Exception {
-        mTestProc = new File(InstrumentationRegistry.getContext().getFilesDir(), "proc");
-        if (mTestProc.exists()) {
-            IoUtils.deleteContents(mTestProc);
-        }
+        mTestProc = TestIoUtils.createTemporaryDirectory("proc");
 
         // The libandroid_servers which have the native method is not available to
         // applications. So in order to have a test support native library, the native code
@@ -85,10 +83,6 @@
     @After
     public void tearDown() throws Exception {
         mFactory = null;
-
-        if (mTestProc.exists()) {
-            IoUtils.deleteContents(mTestProc);
-        }
     }
 
     @Test
diff --git a/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java b/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
index c32c1d2..cebdfe1 100644
--- a/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
+++ b/tests/unit/java/com/android/server/net/NetworkStatsServiceTest.java
@@ -117,7 +117,7 @@
 import com.android.testutils.HandlerUtils;
 import com.android.testutils.TestableNetworkStatsProviderBinder;
 
-import libcore.io.IoUtils;
+import libcore.testing.io.TestIoUtils;
 
 import org.junit.After;
 import org.junit.Before;
@@ -213,10 +213,7 @@
         MockitoAnnotations.initMocks(this);
         final Context context = InstrumentationRegistry.getContext();
         mServiceContext = new MockContext(context);
-        mStatsDir = context.getFilesDir();
-        if (mStatsDir.exists()) {
-            IoUtils.deleteContents(mStatsDir);
-        }
+        mStatsDir = TestIoUtils.createTemporaryDirectory(getClass().getSimpleName());
 
         PowerManager powerManager = (PowerManager) mServiceContext.getSystemService(
                 Context.POWER_SERVICE);
@@ -285,8 +282,6 @@
 
     @After
     public void tearDown() throws Exception {
-        IoUtils.deleteContents(mStatsDir);
-
         mServiceContext = null;
         mStatsDir = null;