WebView Proguard: Keep AwBrowserProcess.sExclusiveFileLock.

android_webview/apk/java/proguard.flags

Index: android_webview/apk/java/proguard.flags
diff --git a/android_webview/apk/java/proguard.flags b/android_webview/apk/java/proguard.flags
index d2034aaec32e6c289b3909a9410b2c5564065a76..0fc784a2f23e52f26e3188f17de1f370335e944a 100644
--- a/android_webview/apk/java/proguard.flags
+++ b/android_webview/apk/java/proguard.flags
@@ -43,6 +43,10 @@
   void onHideCustomView();
 }
 
+-keep class org.chromium.android_webview.AwBrowserProcess {
+    java.nio.channels.FileLock sExclusiveFileLock;
+}
+
 # Accessed via reflection but not present in all builds
 -keep class com.android.webview.chromium.PlatformServiceBridgeGoogle {
   void setMetricsSettingListener(...);