Use mojo from the PDF extension instead of using an extension API.

extensions/common/api/_api_features.json

Index: extensions/common/api/_api_features.json
diff --git a/extensions/common/api/_api_features.json b/extensions/common/api/_api_features.json
index e2412b7f78bc253966a3459cbfc450242105f623..7baee5e11f8b533adff5739aabddc2eefd1fad05 100644
--- a/extensions/common/api/_api_features.json
+++ b/extensions/common/api/_api_features.json
@@ -230,11 +230,7 @@
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "platform_app"]
   },
-  "mimeHandlerPrivate": {
-    "dependencies": ["manifest:mime_types_handler"],
-    "contexts": ["blessed_extension"]
-  },
-  "mojoPrivate": {
+  "mojoPrivate": [{
     "contexts": ["blessed_extension"],
     "channel": "stable",
     "extension_types": ["platform_app", "extension"],
@@ -245,7 +241,10 @@
       "BFEE2E3B80BE21A645E63E9346DFC383E7CB3BDA",
       "63ED55E43214C211F82122ED56407FF1A807F2A3"
     ]
-  },
+  }, {
+    "dependencies": ["manifest:mime_types_handler"],
+    "contexts": ["blessed_extension"]
+  }],
   "networking.config": {
     "dependencies": ["permission:networking.config"],
     "contexts": ["blessed_extension"]