Validate monolithic and modular hidden API flags are consistent

This makes sure that where there is overlap between the hidden API
flags generated for a module and the monolithic flags that they are
identical. That ensures that the modular hidden API flags will be
compatible with previous releases that relied on the monolithic flags.

Bug: 179354495
Test: m out/soong/.intermediates/art/build/boot/art-bootclasspath-fragment/android_common_apex10000/modular-hiddenapi/all-flags.csv
      m out/soong/hiddenapi/hiddenapi-flags.csv
      - Create some inconsistencies between the above two files.
      m out/soong/hiddenapi/hiddenapi-flags.csv.valid
Change-Id: Iaf9e23cef63e221608955d89dc8d496bcc70c86e

scripts/hiddenapi/Android.bp

@@ -47,3 +47,18 @@ python_binary_host {
         },
     },
 }
+
+python_binary_host {
+    name: "verify_overlaps",
+    main: "verify_overlaps.py",
+    srcs: ["verify_overlaps.py"],
+    version: {
+        py2: {
+            enabled: false,
+        },
+        py3: {
+            enabled: true,
+            embedded_launcher: true,
+        },
+    },
+}

scripts/hiddenapi/verify_overlaps.py

@@ -0,0 +1,69 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2018 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Verify that one set of hidden API flags is a subset of another.
+"""
+
+import argparse
+import csv
+
+args_parser = argparse.ArgumentParser(description='Verify that one set of hidden API flags is a subset of another.')
+args_parser.add_argument('all', help='All the flags')
+args_parser.add_argument('subsets', nargs=argparse.REMAINDER, help='Subsets of the flags')
+args = args_parser.parse_args()
+
+
+def dict_reader(input):
+    return csv.DictReader(input, delimiter=',', quotechar='|', fieldnames=['signature'])
+
+# Read in all the flags into a dict indexed by signature
+allFlagsBySignature = {}
+with open(args.all, 'r') as allFlagsFile:
+    allFlagsReader = dict_reader(allFlagsFile)
+    for row in allFlagsReader:
+        signature = row['signature']
+        allFlagsBySignature[signature]=row
+
+failed = False
+for subsetPath in args.subsets:
+    mismatchingSignatures = []
+    with open(subsetPath, 'r') as subsetFlagsFile:
+        subsetReader = dict_reader(subsetFlagsFile)
+        for row in subsetReader:
+            signature = row['signature']
+            if signature in allFlagsBySignature:
+                allFlags = allFlagsBySignature.get(signature)
+                if allFlags != row:
+                    mismatchingSignatures.append((signature, row[None], allFlags[None]))
+            else:
+                mismatchingSignatures.append((signature, row[None], []))
+
+
+    if mismatchingSignatures:
+        failed = True
+        print("ERROR: Hidden API flags are inconsistent:")
+        print("< " + subsetPath)
+        print("> " + args.all)
+        for mismatch in mismatchingSignatures:
+            print()
+            print("< " + mismatch[0] + "," + ",".join(mismatch[1]))
+            if mismatch[2] != None:
+                print("> " + mismatch[0] + "," + ",".join(mismatch[2]))
+            else:
+                print("> " + mismatch[0] + " - missing")
+
+if failed:
+    sys.exit(1)