Refactored TrustAgentUtils to allow agent check injection.

Notes:
- TrustAgentUtils defined a method that allowed callers to determine if a Trust Agent package is allowed to provide trust. If it is, it adds it to the list of available trust agents that can be displayed in the Settings->Security screen.
- The logic used to define what agents are permitted on the device can now be injected.

Test: Ran 'm RunSettingsRoboTest' and added a new test for the TrustAgentFeatureProviderImpl.
Bug: 34354635
Change-Id: I24c54c14bde26073ce6fa907379b86aae2841600

tests/robotests/src/com/android/settings/trustagent/TrustAgentFeatureProviderImplTest.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.trustagent;
+
+import android.content.pm.ResolveInfo;
+import android.content.pm.ServiceInfo;
+import android.content.pm.PackageManager;
+
+import com.android.settings.SettingsRobolectricTestRunner;
+import com.android.settings.TestConfig;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.annotation.Config;
+
+import static junit.framework.Assert.assertFalse;
+import static junit.framework.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public class TrustAgentFeatureProviderImplTest {
+
+    private static final String CANNED_PACKAGE_NAME = "com.test.package";
+
+    @Mock
+    private PackageManager mPackageManager;
+
+    private TrustAgentManagerImpl mImpl;
+
+    @Before
+    public void setUp() throws PackageManager.NameNotFoundException {
+        MockitoAnnotations.initMocks(this);
+        mImpl = new TrustAgentManagerImpl();
+    }
+
+    @Test
+    public void shouldProvideTrust_doesProvideTrustWithPermission() {
+        when(mPackageManager.checkPermission(TrustAgentManager.PERMISSION_PROVIDE_AGENT,
+            CANNED_PACKAGE_NAME)).thenReturn(PackageManager.PERMISSION_GRANTED);
+
+        ServiceInfo serviceInfo = new ServiceInfo();
+        serviceInfo.packageName = CANNED_PACKAGE_NAME;
+        ResolveInfo resolveInfo = new ResolveInfo();
+        resolveInfo.serviceInfo = serviceInfo;
+
+        assertTrue(mImpl.shouldProvideTrust(resolveInfo, mPackageManager));
+    }
+
+    @Test
+    public void shouldProvideTrust_doesNotProvideTrustWithoutPermission() {
+        when(mPackageManager.checkPermission(TrustAgentManager.PERMISSION_PROVIDE_AGENT,
+            CANNED_PACKAGE_NAME)).thenReturn(PackageManager.PERMISSION_DENIED);
+
+        ServiceInfo serviceInfo = new ServiceInfo();
+        serviceInfo.packageName = CANNED_PACKAGE_NAME;
+        ResolveInfo resolveInfo = new ResolveInfo();
+        resolveInfo.serviceInfo = serviceInfo;
+
+        assertFalse(mImpl.shouldProvideTrust(resolveInfo, mPackageManager));
+    }
+}