Support testing for resource shrinking

Add a simple test and add necessary mock dependencies to allow future
resoure shrinking use with platform targets.

Test: m
Bug: 202959019
Change-Id: Id2dd44d52ce5ea62c06784caab0af6276248cb3f
diff --git a/java/dex.go b/java/dex.go
index de36b18..40ee99d 100644
--- a/java/dex.go
+++ b/java/dex.go
@@ -63,6 +63,7 @@
 		// classes referenced by the app manifest.  Defaults to false.
 		No_aapt_flags *bool
 
+		// If true, optimize for size by removing unused resources. Defaults to false.
 		Shrink_resources *bool
 
 		// Flags to pass to proguard.