Remove unused setter

setEnableLowResSnapshots was only added for testing, but it is unused
because we are using a Resource mock to override the value. This is a
better way to test the feature because it ensures expected behavior of
the config overlay.

In addition: remove duplicate test, fix comments for test, and add new
assertions. Also, removed setIsLowResolution in test Builder class to
reflect ActivityManager.TaskSnapshot.Builder.

Test: TaskSnapshotCacheTest
Test: TaskSnapshotControllerTest
Test: TaskSnapshotPersisterLoaderTest
Test: TaskSnapshotSurfaceTest
Bug: 142063079
Change-Id: I83a9503a2f75490e5cf80bdc93041208c4897c6e
diff --git a/services/core/java/com/android/server/wm/TaskSnapshotPersister.java b/services/core/java/com/android/server/wm/TaskSnapshotPersister.java
index 164d3e0..45023ac 100644
--- a/services/core/java/com/android/server/wm/TaskSnapshotPersister.java
+++ b/services/core/java/com/android/server/wm/TaskSnapshotPersister.java
@@ -99,10 +99,10 @@
 
         if (lowResTaskSnapshotScale > 0) {
             mLowResScaleFactor = lowResTaskSnapshotScale / highResTaskSnapshotScale;
-            setEnableLowResSnapshots(true);
+            mEnableLowResSnapshots = true;
         } else {
             mLowResScaleFactor = 0;
-            setEnableLowResSnapshots(false);
+            mEnableLowResSnapshots = false;
         }
 
         mUse16BitFormat = service.mContext.getResources().getBoolean(
@@ -175,14 +175,6 @@
     }
 
     /**
-     * Not to be used. Only here for testing.
-     */
-    @VisibleForTesting
-    void setEnableLowResSnapshots(boolean enabled) {
-        mEnableLowResSnapshots = enabled;
-    }
-
-    /**
      * Return if task snapshots are stored in 16 bit pixel format.
      *
      * @return true if task snapshots are stored in 16 bit pixel format.
@@ -405,7 +397,7 @@
                 return false;
             }
 
-            if (!enableLowResSnapshots()) {
+            if (!mEnableLowResSnapshots) {
                 swBitmap.recycle();
                 return true;
             }