Fixing proguard to not warn about missing class in graphics package.

Change-Id: I894c092beed0e0c8dab4036ab12877fbaf282457
diff --git a/proguard.flags b/proguard.flags
index eb27737..272ab7a 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -50,3 +50,4 @@
 -dontwarn android.app.**
 -dontwarn android.view.**
 -dontwarn android.os.**
+-dontwarn android.graphics.**
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