benchmark: set min sdk version to 28

Bug: 147158171
Test: install and test on device running Android 9 (sdk: 28)
Change-Id: Ieb5b04fc5ccbc4f50377f084f57d88b2bef924c4

media/tests/benchmark/MediaBenchmarkTest/Android.bp

@@ -17,11 +17,13 @@
 android_test {
     name: "MediaBenchmarkTest",
 
+    defaults: [
+        "MediaBenchmark-defaults",
+    ],
+
     // Include all the test code
     srcs: ["src/androidTest/**/*.java"],
 
-    sdk_version: "system_current",
-
     resource_dirs: ["res"],
 
     libs: [
@@ -39,12 +41,22 @@ android_test {
 android_library {
     name: "libMediaBenchmark",
 
+    defaults: [
+        "MediaBenchmark-defaults",
+    ],
+
     // Include all the libraries
     srcs: ["src/main/**/*.java"],
 
-    sdk_version: "system_current",
-
     static_libs: [
         "androidx.test.core",
     ],
 }
+
+java_defaults {
+    name: "MediaBenchmark-defaults",
+
+    sdk_version: "system_current",
+    min_sdk_version: "28",
+    target_sdk_version: "29",
+}