Set the MAXLEN/maxLength attribute for strings in ADM[X] templates.

grit/format/policy_templates/writers/adm_writer.py

Index: grit/format/policy_templates/writers/adm_writer.py
diff --git a/grit/format/policy_templates/writers/adm_writer.py b/grit/format/policy_templates/writers/adm_writer.py
index 27e3433fba1c4a62f7e030be2add72092c06f0ea..16021ecc38c632157530f8ff41f5288147d80f54 100644
--- a/grit/format/policy_templates/writers/adm_writer.py
+++ b/grit/format/policy_templates/writers/adm_writer.py
@@ -122,6 +122,10 @@ class AdmWriter(template_writer.TemplateWriter):
     if policy['type'] == 'int':
       # The default max for NUMERIC values is 9999 which is too small for us.
       builder.AddLine('MIN 0 MAX 2000000000')
+    if policy['type'] in ('string', 'dict'):
+      # The default max for EDITTEXT values is 1023, which is too small for
+      # big JSON blobs and other string policies.
+      builder.AddLine('MAXLEN 1000000')
     if policy['type'] in ('int-enum', 'string-enum'):
       builder.AddLine('ITEMLIST', 1)
       for item in policy['items']: