Move gvr library proguard config to chrome_public_apk_tmpl.gni so that Chrome apk can also use it

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 1c25659a162a01aecaf11ec276cf71fa05ee3166..87adb5cfaf82fb16fad1ed53c6f6544f12ab7c76 100644
--- a/chrome/android/chrome_public_apk_tmpl.gni
+++ b/chrome/android/chrome_public_apk_tmpl.gni
@@ -54,6 +54,10 @@ template("chrome_public_apk_tmpl") {
                            "//base/android/base_proguard_config.flags",
                            "//base/android/release_proguard_config.flags",
                          ]
+      if (enable_webvr) {
+        proguard_configs +=
+            [ "//third_party/gvr-android-sdk/proguard/base.flags" ]
+      }
     }
 
     if (!defined(use_chromium_linker)) {