[DevTools] Interpret 'binary' as 'string' on frontend

This means it's up to the client of the protocol layer to decode
the base64, just like before the introduction of 'binary'.

My overall WIP change is in here, and happy to explain more:
https://chromium-review.googlesource.com/c/chromium/src/+/1244719

Bug: chromium:891377
Change-Id: I60762ff2a815afe2bb0b69480340f1904a1d9909
Reviewed-on: https://chromium-review.googlesource.com/c/1281877
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#600039}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 719629d34caae2c98b184f4a3c96f6cf7edf2e05
diff --git a/scripts/build/code_generator_frontend.py b/scripts/build/code_generator_frontend.py
index 12226dc..8b00f70 100755
--- a/scripts/build/code_generator_frontend.py
+++ b/scripts/build/code_generator_frontend.py
@@ -79,6 +79,8 @@
             return "boolean"
         elif json_type == "string":
             return "string"
+        elif json_type == "binary":
+            return "string"
         elif json_type == "array":
             return "object"
         elif json_type == "object":