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 ce8b74c065839f7f49ec22c8b0dc50fd22c403a2..2b43faefdac432519c6a4f340b904f67f1fa4761 100644
--- a/chrome/android/chrome_public_apk_tmpl.gni
+++ b/chrome/android/chrome_public_apk_tmpl.gni
@@ -14,11 +14,10 @@ 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