avatar: refactor drawing code

Change-Id: I85258ec690aa0d7328d07300e12d9ea1a316ab39
diff --git a/ring-android/app/src/main/res/values/dimens.xml b/ring-android/app/src/main/res/values/dimens.xml
index 341f823..8b62b48 100644
--- a/ring-android/app/src/main/res/values/dimens.xml
+++ b/ring-android/app/src/main/res/values/dimens.xml
@@ -49,4 +49,5 @@
     <dimen name="search_image_card_height">90dp</dimen>
 
     <dimen name="share_preview_height">120dp</dimen>
+    <dimen name="tv_avatar_size">320dp</dimen>
 </resources>
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