Makes separate target for common testing library

Bug: b/297021618
Test: atest ThemePickerTests, WallpaperPickerGoogleTests
Change-Id: I73b5567e04622dc54cea09c17518e75903daf577
diff --git a/Android.bp b/Android.bp
index 4dbe399..9f7dbdb 100644
--- a/Android.bp
+++ b/Android.bp
@@ -66,8 +66,9 @@
         + "$(location soong_zip) -o $(out) -C $$RES_DIR -D $$RES_DIR"
 }
 
+// Common defaults that doesn't have ThemePicker specifics.
 java_defaults {
-    name: "ThemePicker_defaults",
+    name: "ThemePicker_common_defaults",
 
     static_libs: [
         "guava",
@@ -92,7 +93,6 @@
     srcs: [
         ":WallpaperPicker2_srcs",
         ":ThemePicker_srcs",
-        ":ThemePicker_src_overrides",
     ],
 
     required: ["android.software.theme_picker.xml"],
@@ -111,6 +111,12 @@
     system_ext_specific: true,
 }
 
+java_defaults {
+    name: "ThemePicker_defaults",
+    defaults: ["ThemePicker_common_defaults"],
+    srcs: [":ThemePicker_src_overrides"],
+}
+
 prebuilt_etc {
     name: "android.software.theme_picker.xml",
     system_ext_specific: true,