Refactor base's proguard flags to be more usable by cronet

android_webview/system_webview_apk_tmpl.gni

Index: android_webview/system_webview_apk_tmpl.gni
diff --git a/android_webview/system_webview_apk_tmpl.gni b/android_webview/system_webview_apk_tmpl.gni
index 0667b9e8939ed90950896c14e004fe6fb23ab6cf..828263e2b84ddcb54928e4d4a2d63e92a3ac7cf6 100644
--- a/android_webview/system_webview_apk_tmpl.gni
+++ b/android_webview/system_webview_apk_tmpl.gni
@@ -33,8 +33,8 @@ template("system_webview_apk_tmpl") {
       }
       proguard_configs += [
         "//android_webview/apk/java/proguard.flags",
-        "//base/android/base_proguard_config.flags",
-        "//base/android/release_proguard_config.flags",
+        "//base/android/proguard/chromium_apk.flags",
+        "//base/android/proguard/chromium_code.flags",
       ]
     }
   }