[Cronet] Add stamp to api.txt to prevent accidental bulk renames modifying API

Without a stamp a bulk rename could modify the Cronet API but pass through the
API static checks.  With the stamp, edits to api.txt must be done via update_api.py
which enforces the static checks.

Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I01040c5e377bc6a0e8831c2bab30da5d460d6ae3
Reviewed-on: https://chromium-review.googlesource.com/1025644Reviewed-by: Andrei Kapishnikov <kapishnikov@chromium.org>
Commit-Queue: Paul Jensen <pauljensen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553662}

components/cronet/android/api.txt

@@ -295,3 +295,4 @@ public abstract class org.chromium.net.UrlResponseInfo {
   public abstract java.lang.String getProxyServer();
   public abstract long getReceivedByteCount();
 }
+Stamp: f4909b6572d83edd28472e7087b0e6f2

components/cronet/tools/api_static_checks_unittest.py

@@ -8,6 +8,7 @@
 
 import contextlib
 from cStringIO import StringIO
+import md5
 import os
 import shutil
 import sys
@@ -74,7 +75,7 @@ class ApiStaticCheckUnitTest(unittest.TestCase):
     with open(API_VERSION_FILENAME, 'w') as api_version_file:
       api_version_file.write('0')
     with open(API_FILENAME, 'w') as api_file:
-      api_file.write('}\n')
+      api_file.write('}\nStamp: 7d9d25f71cb8a5aba86202540a20d405\n')
     shutil.copytree(os.path.dirname(__file__), 'tools')
 
 
@@ -141,6 +142,15 @@ class ApiStaticCheckUnitTest(unittest.TestCase):
       api_version = api_version_file.read()
     with open(OUT_FILENAME, 'r') as out_file:
       output = out_file.read()
+
+    # Verify stamp
+    api_stamp = api.split('\n')[-2]
+    stamp_length = len('Stamp: 78418460c193047980ae9eabb79293f2\n')
+    api = api[:-stamp_length]
+    api_hash = md5.new()
+    api_hash.update(api)
+    self.assertEquals(api_stamp, 'Stamp: %s' % api_hash.hexdigest())
+
     return [return_code == 0, output, api, api_version]
 
 

components/cronet/tools/update_api.py

@@ -8,6 +8,7 @@
 import argparse
 import filecmp
 import fileinput
+import md5
 import os
 import re
 import shutil
@@ -65,6 +66,7 @@ def generate_api(api_jar, output_filename):
   # Strip out pieces we don't need to compare.
   output_file = fileinput.FileInput(output_filename, inplace=True)
   skip_to_next_class = False
+  md5_hash = md5.new()
   for line in output_file:
     # Skip 'Compiled from ' lines as they're not part of the API.
     if line.startswith('Compiled from "'):
@@ -79,8 +81,11 @@ def generate_api(api_jar, output_filename):
     if skip_to_next_class:
       skip_to_next_class = line != '}'
       continue
+    md5_hash.update(line)
     sys.stdout.write(line)
   output_file.close()
+  with open(output_filename, 'a') as output_file:
+    output_file.write('Stamp: %s\n' % md5_hash.hexdigest())
   return True
 
 
@@ -97,17 +102,40 @@ def check_up_to_date(api_jar):
 
 def check_api_update(old_api, new_api):
   # Enforce that lines are only added when updating API.
+  new_hash = md5.new()
+  old_hash = md5.new()
+  seen_stamp = False
   with open(old_api, 'r') as old_api_file, open(new_api, 'r') as new_api_file:
     for old_line in old_api_file:
       while True:
         new_line = new_api_file.readline()
+        if seen_stamp:
+          print 'ERROR: Stamp is not the last line.'
+          return False
+        if new_line.startswith('Stamp: ') and old_line.startswith('Stamp: '):
+          if old_line != 'Stamp: %s\n' % old_hash.hexdigest():
+            print 'ERROR: Prior api.txt not stamped by update_api.py'
+            return False
+          if new_line != 'Stamp: %s\n' % new_hash.hexdigest():
+            print 'ERROR: New api.txt not stamped by update_api.py'
+            return False
+          seen_stamp = True
+          break
+        new_hash.update(new_line)
         if new_line == old_line:
           break
         if not new_line:
-          print 'ERROR: This API was modified or removed:'
-          print '           ' + old_line
-          print '       Cronet API methods and classes cannot be modified.'
+          if old_line.startswith('Stamp: '):
+            print 'ERROR: New api.txt not stamped by update_api.py'
+          else:
+            print 'ERROR: This API was modified or removed:'
+            print '           ' + old_line
+            print '       Cronet API methods and classes cannot be modified.'
           return False
+      old_hash.update(old_line)
+  if not seen_stamp:
+    print 'ERROR: api.txt not stamped by update_api.py.'
+    return False
   return True