[release] Prepare changelog for 2.0.0-dev.53.0

TBR=whesse@google.com

Change-Id: I780fc63f1efcb433c2b397716e5a72e496ee0d07
Reviewed-on: https://dart-review.googlesource.com/53601
Reviewed-by: Alexander Thomas <athom@google.com>
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0b5662..0872c83 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,8 @@
 
 #### Other Tools
 
+## 2.0.0-dev.53.0
+
 ## 2.0.0-dev.52.0
 
 ### Tool Changes