Only use public fields for triggering clinit

Change-Id: Ic577f142b54eac5d4b6851ed54f1bef607e24c06
diff --git a/src/main/java/com/android/tools/r8/shaking/ClassInitFieldSynthesizer.java b/src/main/java/com/android/tools/r8/shaking/ClassInitFieldSynthesizer.java
index 128a695..7e5847e 100644
--- a/src/main/java/com/android/tools/r8/shaking/ClassInitFieldSynthesizer.java
+++ b/src/main/java/com/android/tools/r8/shaking/ClassInitFieldSynthesizer.java
@@ -46,7 +46,7 @@
     // allocated a single register for the out-value of each ClassInit instruction).
     DexEncodedField encodedClinitField = null;
     for (DexEncodedField staticField : clazz.staticFields()) {
-      if (!staticField.field.type.isWideType()) {
+      if (staticField.isPublic() && !staticField.field.type.isWideType()) {
         encodedClinitField = staticField;
         break;
       }