WebView Proguard: Keep AwBrowserProcess.sExclusiveFileLock.

android_webview/apk/java/proguard.flags

 # Don't rename anything, it makes stack traces unintelligible. We only allow the
 # obfuscation pass to run so that we can discard attributes like local variable
 # tables. However, we don't want to lose out on optimizations, so although they
 # can occasionally make the stack trace a bit stranger with inlining, it won't
 # make a big difference for the users seeing the stacktraces. We can always use
 # build/android/stacktrace/java_deobfuscate.py to fix the stacktrace up for us.
 -keepnames,allowoptimization class *** { *; }
 
 # Keep the factory and its public members; it's the main entry point used by the
 # framework.
@@ skipping 25 matching lines @@
 # android.net.ProxyProperties.
 -dontnote org.chromium.net.ProxyChangeListener$ProxyReceiver
 
 # Silence warnings about reflection used to check for onShow/HideCustomView.
 # This class is not really kept since it's in a library jar.
 -keep class android.webkit.WebChromeClient {
   void onShowCustomView(...);
   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(...);
   PlatformServiceBridgeGoogle(...);
 }
 -dontnote com.android.webview.chromium.PlatformServiceBridgeGoogle
 
 #TODO(hush): remove after N release. crbug.com/546762
 -keep class com.android.webview.chromium.ContentSettingsAdapter {
   public void setDisabledActionModeMenuItems(int);
   public int getDisabledActionModeMenuItems();
 }