[Android] memory_inspector: update PRESUBMIT.py to check prebuilts.

Add a PRESUBMIT check to verify that all prebuilts are actually
deployed to GCS (i.e. the committer didn't forget to run
upload_to_google_storage.py).

BUG=340294
NOTRY=true

Review URL: https://codereview.chromium.org/562553003

Cr-Commit-Position: refs/heads/master@{#295057}

tools/memory_inspector/PRESUBMIT.py

@@ -9,7 +9,7 @@ details on the presubmit API built into gcl.
 """
 
 
-def CommonChecks(input_api, output_api):
+def _CommonChecks(input_api, output_api):
   output = []
   blacklist = [r'classification_rules.*']
   output.extend(input_api.canned_checks.RunPylint(
@@ -30,9 +30,55 @@ def CommonChecks(input_api, output_api):
   return output
 
 
+def _CheckPrebuiltsAreUploaded(input_api, output_api):
+  """Checks that the SHA1 files in prebuilts/ reference existing objects on GCS.
+
+  This is to avoid that somebody accidentally checks in some new XXX.sha1 files
+  into prebuilts/ without having previously uploaded the corresponding binaries
+  to the cloud storage bucket. This can happen if the developer has a consistent
+  local copy of the binary. This check verifies (through a HTTP HEAD request)
+  that the GCS bucket has an object for each .sha1 file in prebuilts and raises
+  a presubmit error, listing the missing files, if not.
+  """
+  import sys
+  import urllib2
+  old_sys_path = sys.path
+  try:
+    sys.path = [input_api.PresubmitLocalPath()] + sys.path
+    from memory_inspector import constants
+  finally:
+    sys.path = old_sys_path
+  missing_files = []
+  for f in input_api.os_listdir(constants.PREBUILTS_PATH):
+    if not f.endswith('.sha1'):
+      continue
+    prebuilt_sha_path = input_api.os_path.join(constants.PREBUILTS_PATH, f)
+    with open(prebuilt_sha_path) as sha_file:
+      sha = sha_file.read().strip()
+    url = constants.PREBUILTS_BASE_URL + sha
+    request = urllib2.Request(url)
+    request.get_method = lambda : 'HEAD'
+    try:
+      urllib2.urlopen(request, timeout=5)
+    except Exception as e:
+      if isinstance(e, urllib2.HTTPError) and e.code == 404:
+        missing_files += [prebuilt_sha_path]
+      else:
+        return [output_api.PresubmitError('HTTP Error while checking %s' % url,
+                                          long_text=str(e))]
+  if missing_files:
+    return [output_api.PresubmitError(
+        'Some prebuilts have not been uploaded. Perhaps you forgot to '
+        'upload_to_google_storage.py?', missing_files)]
+  return []
+
+
 def CheckChangeOnUpload(input_api, output_api):
-  return CommonChecks(input_api, output_api)
+  results = []
+  results.extend(_CommonChecks(input_api, output_api))
+  results.extend(_CheckPrebuiltsAreUploaded(input_api, output_api))
+  return results
 
 
 def CheckChangeOnCommit(input_api, output_api):
-  return CommonChecks(input_api, output_api)
+  return _CommonChecks(input_api, output_api)