Protect animation methods from Proguard.

Bug: 5096417
Change-Id: I5546dfe0092747c311836bb2134b52be58d77b98
diff --git a/packages/SystemUI/proguard.flags b/packages/SystemUI/proguard.flags
index 5e48461..fe5b983 100644
--- a/packages/SystemUI/proguard.flags
+++ b/packages/SystemUI/proguard.flags
@@ -4,3 +4,12 @@
   public void recentButtonClicked(android.view.View);
   public void toggleLightsOut(android.view.View);
 }
+
+-keep class com.android.systemui.statusbar.policy.KeyButtonView {
+  public float getDrawingAlpha();
+  public float getGlowAlpha();
+  public float getGlowScale();
+  public void setDrawingAlpha(float);
+  public void setGlowAlpha(float);
+  public void setGlowScale(float);
+}