Replace ImageDecoder.sApiLevel with a SystemApi helper

Bug: 152322291
Test: CtsGraphicsTestCases

ImageDecoder is moving to a mainline module, so the system can no longer
access the @hidden sApiLevel without making it @SystemApi. Instead of
promoting the existing API, provide a common class to be used by any UI
rendering class that needs to access the targetSdkVersion. Switch AVD to
use the new class, which is a SystemApi.

Change-Id: Ie7172fb93364a1e04ab844b8fa64887bf9d8b005

graphics/java/android/graphics/ImageDecoder.java

@@ -171,9 +171,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
  *  </pre>
  */
 public final class ImageDecoder implements AutoCloseable {
-    /** @hide **/
-    public static int sApiLevel;
-
     /**
      *  Source of encoded image data.
      *
@@ -1933,7 +1930,8 @@ public final class ImageDecoder implements AutoCloseable {
 
         // For P and above, only resize if it would be a downscale. Scale up prior
         // to P in case the app relies on the Bitmap's size without considering density.
-        if (srcDensity < dstDensity && sApiLevel >= Build.VERSION_CODES.P) {
+        if (srcDensity < dstDensity
+                && Compatibility.getTargetSdkVersion() >= Build.VERSION_CODES.P) {
             return srcDensity;
         }