Android: Make NativeLibraries.java fields final

I was hoping this would remove
NativeLibraries.getTestRunnerClassNameForTesting()
but it doesn't look like it does :(.

Still - this way of creating the file brings it in line with how
we create R.java and BuildConfig.java.

Bug: 984573
Change-Id: Iebeaa9970ac9c47ea13f81f05b71d5ccb5247205
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704315
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678569}

base/BUILD.gn

@@ -3504,6 +3504,7 @@ if (is_android) {
   }
 
   write_native_libraries_java("base_native_libraries_gen") {
+    use_final_fields = false
   }
 
   android_library("base_java_unittest_support") {

build/android/gyp/native_libraries_template.py

@@ -10,61 +10,21 @@ NATIVE_LIBRARIES_TEMPLATE = """\
 package org.chromium.base.library_loader;
 
 public class NativeLibraries {{
-    /**
-     * IMPORTANT NOTE: The variables defined here must _not_ be 'final'.
-     *
-     * The reason for this is very subtle:
-     *
-     * - This template is used to generate several distinct, but similar
-     *   files used in different contexts:
-     *
-     *   o .../gen/templates/org/chromium/base/library_loader/NativeLibraries.java
-     *
-     *     This file is used to build base.jar, which is the library
-     *     jar used by chromium projects. However, the
-     *     corresponding NativeLibraries.class file will _not_ be part
-     *     of the final base.jar.
-     *
-     *   o .../$PROJECT/native_libraries_java/NativeLibraries.java
-     *
-     *     This file is used to build an APK (e.g. $PROJECT
-     *     could be 'content_shell_apk'). Its content will depend on
-     *     this target's specific build configuration, and differ from
-     *     the source file above.
-     *
-     * - During the final link, all .jar files are linked together into
-     *   a single .dex file, and the second version of NativeLibraries.class
-     *   will be put into the final output file, and used at runtime.
-     *
-     * - If the variables were defined as 'final', their value would be
-     *   optimized out inside of 'base.jar', and could not be specialized
-     *   for every chromium program. This, however, doesn't apply to arrays of
-     *   strings, which can be defined as final.
-     *
-     * This exotic scheme is used to avoid injecting project-specific, or
-     * even build-specific, values into the base layer. E.g. this is
-     * how the component build is supported on Android without modifying
-     * the sources of each and every Chromium-based target.
-     */
-
     public static final int CPU_FAMILY_UNKNOWN = 0;
     public static final int CPU_FAMILY_ARM = 1;
     public static final int CPU_FAMILY_MIPS = 2;
     public static final int CPU_FAMILY_X86 = 3;
 
     // Set to true to enable the use of the Chromium Linker.
-    public static boolean sUseLinker{USE_LINKER};
-    public static boolean sUseLibraryInZipFile{USE_LIBRARY_IN_ZIP_FILE};
-    public static boolean sEnableLinkerTests{ENABLE_LINKER_TESTS};
+    public static {MAYBE_FINAL}boolean sUseLinker{USE_LINKER};
+    public static {MAYBE_FINAL}boolean sUseLibraryInZipFile{USE_LIBRARY_IN_ZIP_FILE};
+    public static {MAYBE_FINAL}boolean sEnableLinkerTests{ENABLE_LINKER_TESTS};
 
     // This is the list of native libraries to be loaded (in the correct order)
-    // by LibraryLoader.java.  The base java library is compiled with no
-    // array defined, and then the build system creates a version of the file
-    // with the real list of libraries required (which changes based upon which
-    // .apk is being built).
+    // by LibraryLoader.java.
     // TODO(cjhopman): This is public since it is referenced by NativeTestActivity.java
     // directly. The two ways of library loading should be refactored into one.
-    public static final String[] LIBRARIES = {LIBRARIES};
+    public static {MAYBE_FINAL}String[] LIBRARIES = {LIBRARIES};
 
     // This is the expected version of the 'main' native library, which is the one that
     // implements the initial set of base JNI functions including
@@ -72,8 +32,8 @@ public class NativeLibraries {{
     // TODO(torne): This is public to work around classloader issues in Trichrome
     // where NativeLibraries is not in the same dex as LibraryLoader.
     // We should instead split up Java code along package boundaries.
-    public static String sVersionNumber = {VERSION_NUMBER};
+    public static {MAYBE_FINAL}String sVersionNumber = {VERSION_NUMBER};
 
-    public static int sCpuFamily = {CPU_FAMILY};
+    public static {MAYBE_FINAL}int sCpuFamily = {CPU_FAMILY};
 }}
 """

build/android/gyp/write_native_libraries_java.py

@@ -15,13 +15,10 @@ from native_libraries_template import NATIVE_LIBRARIES_TEMPLATE
 from util import build_utils
 
 
-def _GetFormattedBoolean(value):
-  return ' = true' if value else ''
-
-
 def main():
   parser = argparse.ArgumentParser()
 
+  parser.add_argument('--final', action='store_true', help='Use final fields.')
   parser.add_argument(
       '--enable-chromium-linker',
       action='store_true',
@@ -77,19 +74,21 @@ def main():
   native_libraries_list = (
       '{%s}' % ','.join(['"%s"' % s[3:-3] for s in lib_paths]))
 
+  def bool_str(value):
+    if value:
+      return ' = true'
+    elif options.final:
+      return ' = false'
+    return ''
+
   format_dict = {
-      'USE_LINKER':
-      _GetFormattedBoolean(options.enable_chromium_linker),
-      'USE_LIBRARY_IN_ZIP_FILE':
-      _GetFormattedBoolean(options.load_library_from_apk),
-      'ENABLE_LINKER_TESTS':
-      _GetFormattedBoolean(options.enable_chromium_linker_tests),
-      'LIBRARIES':
-      native_libraries_list,
-      'VERSION_NUMBER':
-      options.version_number,
-      'CPU_FAMILY':
-      options.cpu_family,
+      'MAYBE_FINAL': 'final ' if options.final else '',
+      'USE_LINKER': bool_str(options.enable_chromium_linker),
+      'USE_LIBRARY_IN_ZIP_FILE': bool_str(options.load_library_from_apk),
+      'ENABLE_LINKER_TESTS': bool_str(options.enable_chromium_linker_tests),
+      'LIBRARIES': native_libraries_list,
+      'VERSION_NUMBER': options.version_number,
+      'CPU_FAMILY': options.cpu_family,
   }
   with build_utils.AtomicOutput(options.output) as f:
     with zipfile.ZipFile(f.name, 'w') as srcjar_file:

build/config/android/rules.gni

@@ -722,6 +722,8 @@ if (enable_java_templates) {
   #   enable_chromium_linker_tests: (Optional) Whether to run tests.
   #   dont_load_shared_libraries: (Optional) List of native libraries to exclude
   #     from output.
+  #   use_final_fields: True to use final fields. When false, all other
+  #       variables must not be set.
   template("write_native_libraries_java") {
     _native_libraries_file = "$target_gen_dir/$target_name.srcjar"
     if (current_cpu == "arm" || current_cpu == "arm64") {
@@ -750,38 +752,39 @@ if (enable_java_templates) {
         "--cpu-family",
         _cpu_family,
       ]
-      if (defined(invoker.native_libraries_list_file)) {
+      if (invoker.use_final_fields) {
         args += [
+          "--final",
           "--native-libraries-list",
           rebase_path(invoker.native_libraries_list_file, root_build_dir),
         ]
         inputs = [
           invoker.native_libraries_list_file,
         ]
-      }
-      if (defined(invoker.version_number)) {
-        args += [
-          "--version-number",
-          invoker.version_number,
-        ]
-      }
-      if (defined(invoker.enable_chromium_linker) &&
-          invoker.enable_chromium_linker) {
-        args += [ "--enable-chromium-linker" ]
-      }
-      if (defined(invoker.load_library_from_apk) &&
-          invoker.load_library_from_apk) {
-        args += [ "--load-library-from-apk" ]
-      }
-      if (defined(invoker.enable_chromium_linker_tests) &&
-          invoker.enable_chromium_linker_tests) {
-        args += [ "--enable-chromium-linker-tests" ]
-      }
+        if (defined(invoker.version_number)) {
+          args += [
+            "--version-number",
+            invoker.version_number,
+          ]
+        }
+        if (defined(invoker.enable_chromium_linker) &&
+            invoker.enable_chromium_linker) {
+          args += [ "--enable-chromium-linker" ]
+        }
+        if (defined(invoker.load_library_from_apk) &&
+            invoker.load_library_from_apk) {
+          args += [ "--load-library-from-apk" ]
+        }
+        if (defined(invoker.enable_chromium_linker_tests) &&
+            invoker.enable_chromium_linker_tests) {
+          args += [ "--enable-chromium-linker-tests" ]
+        }
 
-      # TODO(tiborg): Remove once all usages are removed.
-      if (defined(invoker.dont_load_shared_libraries)) {
-        args += [ "--exclude-native-libraries=" +
-                  invoker.dont_load_shared_libraries ]
+        # TODO(tiborg): Remove once all usages are removed.
+        if (defined(invoker.dont_load_shared_libraries)) {
+          args += [ "--exclude-native-libraries=" +
+                    invoker.dont_load_shared_libraries ]
+        }
       }
     }
   }
@@ -1940,8 +1943,8 @@ if (enable_java_templates) {
   # apks that depend on //base:base_java.
   #
   # Variables:
-  #   use_final_fields: True to use final fields. All other variables are
-  #       ignored when this is false.
+  #   use_final_fields: True to use final fields. When false, all other
+  #       variables must not be set.
   #   enable_multidex: Value for ENABLE_MULTIDEX.
   #   min_sdk_version: Value for MIN_SDK_VERSION.
   #
@@ -2663,6 +2666,7 @@ if (enable_java_templates) {
         }
         enable_chromium_linker = _use_chromium_linker
         load_library_from_apk = _load_library_from_apk
+        use_final_fields = true
       }
       _srcjar_deps += [ ":${_template_name}__native_libraries" ]
     }