Reland of GN: Enable proguard for apks

chrome/android/chrome_public_apk_tmpl.gni

Index: chrome/android/chrome_public_apk_tmpl.gni
diff --git a/chrome/android/chrome_public_apk_tmpl.gni b/chrome/android/chrome_public_apk_tmpl.gni
index b068b39efe626b856724b6ae8ce0c949cd5bf2b5..a193908c328f7dbff9d938660ebf19f3ce3e312b 100644
--- a/chrome/android/chrome_public_apk_tmpl.gni
+++ b/chrome/android/chrome_public_apk_tmpl.gni
@@ -13,11 +13,10 @@ template("chrome_public_apk_tmpl") {
         rebase_path("$root_gen_dir/CHROME_VERSION.json", root_out_dir)
     native_lib_version_arg = "@FileArg($_native_lib_file:full-quoted)"
 
-    # TODO(GYP):
-    #'proguard_enabled': 'true',
-    #'proguard_flags_paths': [
-    #  'chrome/android/java/proguard.flags',
-    #]
+    if (!is_debug) {
+      proguard_enabled = true
+      proguard_configs = [ "//chrome/android/java/proguard.flags" ]
+    }
 
     if (chromium_linker_supported) {
       use_chromium_linker = true