[Android] Rework multidex and enable multidex for unit_tests_apk.

build/android/gyp/configure_multidex.py

Index: build/android/gyp/configure_multidex.py
diff --git a/build/android/gyp/configure_multidex.py b/build/android/gyp/configure_multidex.py
index aa85d2ffb165546577e8464e20a2134cdd5bf191..9f3b7360f7132bfd7281f4881f497c620ecc4502 100755
--- a/build/android/gyp/configure_multidex.py
+++ b/build/android/gyp/configure_multidex.py
@@ -6,23 +6,33 @@
 
 import argparse
 import json
+import os
 import sys
 
 from util import build_utils
 
 
+_GCC_PREPROCESS_PATH = os.path.join(
+    os.path.dirname(__file__), 'gcc_preprocess.py')
+
+
 def ParseArgs():
   parser = argparse.ArgumentParser()
   parser.add_argument('--configuration-name', required=True,
                       help='The build CONFIGURATION_NAME.')
+  parser.add_argument('--enable-multidex', action='store_true', default=False,
+                      help='If passed, multidex may be enabled.')
   parser.add_argument('--enabled-configurations', default=[],
                       help='The configuration(s) for which multidex should be '
                            'enabled. If not specified and --enable-multidex is '
                            'passed, multidex will be enabled for all '
-                            'configurations.')
+                           'configurations.')
   parser.add_argument('--multidex-configuration-path', required=True,
                       help='The path to which the multidex configuration JSON '
                            'should be saved.')
+  parser.add_argument('--multidex-config-java-file', required=True)
+  parser.add_argument('--multidex-config-java-stamp', required=True)
+  parser.add_argument('--multidex-config-java-template', required=True)
 
   args = parser.parse_args()
 
@@ -33,20 +43,42 @@ def ParseArgs():
   return args
 
 
-def main():
-  args = ParseArgs()
-
-  multidex_enabled = (
-      (not args.enabled_configurations
-       or args.configuration_name in args.enabled_configurations))
-
+def _WriteConfigJson(multidex_enabled, multidex_configuration_path):
   config = {
     'enabled': multidex_enabled,
   }
 
-  with open(args.multidex_configuration_path, 'w') as f:
+  with open(multidex_configuration_path, 'w') as f:
     f.write(json.dumps(config))
 
+
+def _GenerateMultidexConfigJava(multidex_enabled, args):
+  gcc_preprocess_cmd = [
+    sys.executable, _GCC_PREPROCESS_PATH,
+    '--include-path=',
+    '--template', args.multidex_config_java_template,
+    '--stamp', args.multidex_config_java_stamp,
+    '--output', args.multidex_config_java_file,
+  ]
+  if multidex_enabled:
+    gcc_preprocess_cmd += [
+      '--defines', 'ENABLE_MULTIDEX',
+    ]
+
+  build_utils.CheckOutput(gcc_preprocess_cmd)
+
+
+def main():
+  args = ParseArgs()
+
+  multidex_enabled = (
+      args.enable_multidex
+      and (not args.enabled_configurations
+           or args.configuration_name in args.enabled_configurations))
+
+  _WriteConfigJson(multidex_enabled, args.multidex_configuration_path)
+  _GenerateMultidexConfigJava(multidex_enabled, args)
+
   return 0