Add GN template for android_assets(). Use it in content_shell_apk.

build/android/gyp/write_build_config.py

Index: build/android/gyp/write_build_config.py
diff --git a/build/android/gyp/write_build_config.py b/build/android/gyp/write_build_config.py
index 340d23f15f8cdc5873baf3f22d8c6210fa515e29..736f9a6f48d999d675e7812e72e3e8c5dc099658 100755
--- a/build/android/gyp/write_build_config.py
+++ b/build/android/gyp/write_build_config.py
@@ -129,6 +129,11 @@ def main(argv):
       help='Java package name for these resources.')
   parser.add_option('--android-manifest', help='Path to android manifest.')
 
+  # android_assets options
+  parser.add_option('--assets', help='List of asset\'s sources.')
+  parser.add_option('--disable-asset-compression', action='store_true',
+                    help='Whether to enable asset compression.')
+
   # java library options
   parser.add_option('--jar-path', help='Path to target\'s jar output.')
   parser.add_option('--supports-android', action='store_true',
@@ -154,18 +159,17 @@ def main(argv):
   if args:
     parser.error('No positional arguments should be given.')
 
-
-  if not options.type in [
-      'java_library', 'android_resources', 'android_apk', 'deps_dex']:
+  required_options_map = {
+      'java_library': ['build_config', 'jar_path'],
+      'android_assets': ['build_config', 'assets'],
+      'android_resources': ['build_config', 'resources_zip'],
+      'android_apk': ['build_config', 'jar_path', 'dex_path', 'resources_zip'],
+      'deps_dex': ['build_config', 'dex_path']
+  }
+  required_options = required_options_map.get(options.type)
+  if not required_options:
     raise Exception('Unknown type: <%s>' % options.type)
 
-  required_options = ['build_config'] + {
-      'java_library': ['jar_path'],
-      'android_resources': ['resources_zip'],
-      'android_apk': ['jar_path', 'dex_path', 'resources_zip'],
-      'deps_dex': ['dex_path']
-    }[options.type]
-
   if options.native_libs:
     required_options.append('readelf_path')
 
@@ -182,8 +186,8 @@ def main(argv):
   possible_deps_config_paths = build_utils.ParseGypList(
       options.possible_deps_configs)
 
-  allow_unknown_deps = (options.type == 'android_apk' or
-                        options.type == 'android_resources')
+  allow_unknown_deps = (options.type in
+                        ('android_apk', 'android_assets', 'android_resources'))
   unknown_deps = [
       c for c in possible_deps_config_paths if not os.path.exists(c)]
   if unknown_deps and not allow_unknown_deps:
@@ -262,6 +266,12 @@ def main(argv):
     # Apks will get their resources srcjar explicitly passed to the java step.
     config['javac']['srcjars'] = []
 
+  if options.type == 'android_assets':
+    deps_info['assets'] = {
+        'paths': build_utils.ParseGypList(options.assets),
+        'enable_compression': not options.disable_asset_compression
+    }
+
   if options.type == 'android_resources':
     deps_info['resources_zip'] = options.resources_zip
     if options.srcjar:
@@ -358,6 +368,8 @@ def main(argv):
       'libraries': library_paths,
       'java_libraries_list': java_libraries_list_holder[0],
     }
+    all_assets = deps.All('android_assets')
+    config['merged_assets'] = [a['assets'] for a in all_assets if 'assets' in a]
 
   build_utils.WriteJson(config, options.build_config, only_if_changed=True)