Make use of md5_check within write_build_config.py

build/android/gyp/write_build_config.py

 #!/usr/bin/env python
 #
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Writes a build_config file.
 
 The build_config file for a target is a json file containing information about
 how to build that target based on the target's dependencies. This includes
@@ skipping 14 matching lines @@
     a. inputs/deps ensure that the action runs whenever one of the files changes
     b. the files are added to the action's depfile
 """
 
 import optparse
 import os
 import sys
 import xml.dom.minidom
 
 from util import build_utils
+from util import md5_check
 
 import write_ordered_libraries
 
 class AndroidManifest(object):
   def __init__(self, path):
     self.path = path
     dom = xml.dom.minidom.parse(path)
     manifests = dom.getElementsByTagName('manifest')
     assert len(manifests) == 1
     self.manifest = manifests[0]
@@ skipping 271 matching lines @@
         c['jar_path'] for c in all_library_deps
       ]
     }
     manifest = AndroidManifest(options.android_manifest)
     deps_info['package_name'] = manifest.GetPackageName()
     if not options.tested_apk_config and manifest.GetInstrumentation():
       # This must then have instrumentation only for itself.
       manifest.CheckInstrumentation(manifest.GetPackageName())
 
     library_paths = []
-    java_libraries_list = []
-    if options.native_libs:
-      libraries = build_utils.ParseGypList(options.native_libs)
-      if libraries:
+    java_libraries_list_holder = [None]
+    libraries = build_utils.ParseGypList(options.native_libs or '[]')
+    if libraries:
+      def recompute_ordered_libraries():
         libraries_dir = os.path.dirname(libraries[0])
         write_ordered_libraries.SetReadelfPath(options.readelf_path)
         write_ordered_libraries.SetLibraryDirs([libraries_dir])
-        all_native_library_deps = (
+        all_deps = (
             write_ordered_libraries.GetSortedTransitiveDependenciesForBinaries(
                 libraries))
         # Create a java literal array with the "base" library names:
         # e.g. libfoo.so -> foo
-        java_libraries_list = '{%s}' % ','.join(
-            ['"%s"' % s[3:-3] for s in all_native_library_deps])
-        library_paths = map(
-            write_ordered_libraries.FullLibraryPath, all_native_library_deps)
+        java_libraries_list_holder[0] = ('{%s}' % ','.join(
+            ['"%s"' % s[3:-3] for s in all_deps]))
+        library_paths.extend(
+            write_ordered_libraries.FullLibraryPath(x) for x in all_deps)
 
-      config['native'] = {
-        'libraries': library_paths,
-        'java_libraries_list': java_libraries_list
-      }
+      # This step takes about 600ms on a z620 for chrome_apk, so it's worth
+      # caching.
+      md5_check.CallAndRecordIfStale(
+          recompute_ordered_libraries,
+          record_path=options.build_config + '.nativelibs.md5.stamp',
+          input_paths=libraries,
+          output_paths=[options.build_config])
+      if not library_paths:
+        prev_config = build_utils.ReadJson(options.build_config)
+        java_libraries_list_holder[0] = (
+            prev_config['native']['java_libraries_list'])
+        library_paths.extend(prev_config['native']['libraries'])
+
+    config['native'] = {
+      'libraries': library_paths,
+      'java_libraries_list': java_libraries_list_holder[0],
+    }
 
   build_utils.WriteJson(config, options.build_config, only_if_changed=True)
 
   if options.depfile:
     build_utils.WriteDepfile(
         options.depfile,
         deps.AllConfigPaths() + build_utils.GetPythonDependencies())
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))