ui: add gae internal server code

This is the internal Google extension server. Very simple, just serving
straight out of a GCS bucket.

Author: LalitMaganti

infra/gae-internal/.gcloudignore

@@ -0,0 +1,19 @@
+# This file specifies files that are *not* uploaded to Google Cloud
+# using gcloud. It follows the same syntax as .gitignore, with the addition of
+# "#!include" directives (which insert the entries of the given .gitignore-style
+# file at that point).
+#
+# For more information, run:
+#   $ gcloud topic gcloudignore
+#
+.gcloudignore
+# If you would like to upload your .git directory, .gitignore file or files
+# from your .gitignore file, remove the corresponding line
+# below:
+.git
+.gitignore
+
+# Python pycache:
+__pycache__/
+# Ignored by the build system
+/setup.cfg

infra/gae-internal/app.yaml

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+runtime: python312
+
+entrypoint: gunicorn -b :$PORT main:app
+
+instance_class: F1
+
+automatic_scaling:
+  max_instances: 2

infra/gae-internal/deploy

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+#!/bin/bash
+gcloud app deploy app.yaml --project google.com:perfetto-gae-internal
+

infra/gae-internal/main.py

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+import posixpath
+
+from flask import Flask, Response, abort
+from flask_cors import CORS
+from google.cloud import storage
+
+app = Flask(__name__)
+CORS(app, origins=["https://ui.perfetto.dev", "http://localhost:10000"], supports_credentials=True)
+
+BUCKET_NAME = "perfetto-ui-internal"
+BASE_PREFIX = "extension-server-v1"
+
+gcs_client = storage.Client()
+bucket = gcs_client.bucket(BUCKET_NAME)
+
+
+@app.route("/", defaults={"path": ""})
+@app.route("/<path:path>")
+def serve(path):
+    # Normalize and reject any path traversal attempts.
+    normalized = posixpath.normpath(path) if path else ""
+    if normalized.startswith("..") or "/../" in normalized or normalized.startswith("/"):
+        abort(403)
+
+    blob_path = f"{BASE_PREFIX}/{normalized}" if normalized else BASE_PREFIX + "/"
+
+    blob = bucket.blob(blob_path)
+    if not blob.exists():
+        abort(404)
+
+    data = blob.download_as_bytes()
+    content_type = blob.content_type or "application/octet-stream"
+    return Response(data, content_type=content_type)
+
+
+if __name__ == "__main__":
+    app.run(host="127.0.0.1", port=8080, debug=True)

infra/gae-internal/requirements.txt

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+Flask==3.0.0
+Flask-Cors==4.0.0
+google-cloud-storage==2.14.0
+gunicorn==21.2.0