SuperSize: Improve deploy documentation

And have upload_html_viewer.py check that caspian files exist

Bug: None
Change-Id: I9775e5c983cbb8d4a4aa4b74037eee88dffcee99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2387400
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803372}

tools/binary_size/libsupersize/caspian/README.md

@@ -10,7 +10,7 @@ Install emscripten from:
 https://emscripten.org/docs/getting_started/downloads.html
 
 ```sh
-git apply tools/binary_size/libsupersize/caspian/wasmbuild.patch
+git apply -3 tools/binary_size/libsupersize/caspian/wasmbuild.patch
 gn gen out/caspian --args='is_official_build=true treat_warnings_as_errors=false fatal_linker_warnings=false'
 ( cd out/caspian; autoninja tools/binary_size:caspian_web && cp wasm/caspian_web.* ../../tools/binary_size/libsupersize/static/ )
 ```
@@ -22,5 +22,5 @@ tools/binary_size/supersize start_server out.size
 
 or upload to hosted site via:
 ```sh
-tools/binary_size/libsupersize/upload_html_viewer.py --sync
+tools/binary_size/libsupersize/upload_html_viewer.py
 ```

tools/binary_size/libsupersize/upload_html_viewer.py

@@ -57,6 +57,8 @@ def _FirebaseDeploy(project_dir):
 def _CopyStaticFiles(project_static_dir):
   """Copy over static files from the static directory."""
   static_files = os.path.join(os.path.dirname(__file__), 'static')
+  if not os.path.exists(os.path.join(static_files, 'caspian_web.js')):
+    raise Exception('static/caspian_web.js is missing. See caspian/README.md')
   shutil.copytree(static_files, project_static_dir)
 
 
@@ -78,7 +80,7 @@ def _Prompt(message):
 
 def main():
   message = (
-"""This script deploys the contents of //tools/binary_size/libsupersize/static
+  """This script deploys the contents of //tools/binary_size/libsupersize/static
 to firebase hosting at chrome-supersize.firebaseapp.com. Please ensure you have
 read the instructions at //tools/binary_size/libsupersize/static/README.md first
 before running this. Are you sure you want to continue?""")