Fix tools/gen_binary_descriptors

- Actually run tool in presubmit
- Improve error messages
- Optionally find protoc automatically
- Update perfetto_config.descriptor.h

Change-Id: I13e6880b7d3f86464acfbb6a9134e2055ca860a6
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 9a4902f..3c11c8b 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -30,6 +30,7 @@
     results += input.canned_checks.CheckGNFormatted(input, output)
     results += CheckIncludeGuards(input, output)
     results += CheckAndroidBlueprint(input, output)
+    results += CheckBinaryDescriptors(input, output)
     results += CheckMergedTraceConfigProto(input, output)
     results += CheckWhitelist(input, output)
     return results
@@ -85,7 +86,7 @@
     tool = 'tools/gen_binary_descriptors'
     file_filter = lambda x: input_api.FilterSourceFile(
           x,
-          white_list=('.*[.]h$', '.*[.]proto$', tool))
+          white_list=('protos/perfetto/.*[.]proto$', '.*[.]h', tool))
     if not input_api.AffectedSourceFiles(file_filter):
         return []
     if subprocess.call([tool, '--check-only']):