Use floating-point value for Drawable level

This allows us to run fine-grained level animations.

Backwards compatibility:
Another CL will add DrawableCompat.setLevel(float) to forward calls to
the existing integer-based method. For callbacks, developers can override
onLevelChanged(int) and use DrawableCompat.getLevelFloat() to obtain the
floating-point level. Overriding onLevelChanged(float) will only work on
current API.

Bug: 23566299
Change-Id: I431fe6f3679c8f23f9cf3c2bb1f92a4059ee68e3

graphics/java/android/graphics/drawable/DrawableWrapper.java

@@ -92,7 +92,7 @@ public abstract class DrawableWrapper extends Drawable implements Drawable.Callb
             // Only call setters for data that's stored in the base Drawable.
             dr.setVisible(isVisible(), true);
             dr.setState(getState());
-            dr.setLevel(getLevel());
+            dr.setLevel(getLevelFloat());
             dr.setBounds(getBounds());
             dr.setLayoutDirection(getLayoutDirection());
 
@@ -286,7 +286,7 @@ public abstract class DrawableWrapper extends Drawable implements Drawable.Callb
     }
 
     @Override
-    protected boolean onLevelChange(int level) {
+    protected boolean onLevelChange(float level) {
         return mDrawable != null && mDrawable.setLevel(level);
     }