Add missing dependencies to the background image app (flutter#30769)

Author: Emmanuel Garcia

testing/android_background_image/android/app/build.gradle

@@ -45,8 +45,17 @@ android {
 }
 
 dependencies {
+    // Please *don't* add embedding dependencies to this file.
+    // The embedding dependencies are configured in tools/androidx/files.json.
+    // Only add test dependencies.
+
     implementation files(project.property('flutter_jar'))
-    implementation 'androidx.appcompat:appcompat:1.1.0'
-    implementation 'androidx.lifecycle:lifecycle-common-java8:2.2.0-alpha01'
-    implementation 'androidx.tracing:tracing:1.0.0'
+}
+
+// Configure the embedding dependencies.
+apply from: new File(rootDir, '../../../tools/androidx/configure.gradle').absolutePath;
+configureDependencies(new File(rootDir, '../../..')) { dependency ->
+    dependencies {
+        implementation "$dependency"
+    }
 }