[Android WebView] Propagate Java exceptions from handleJsBeforeUnload.

android_webview/java/src/org/chromium/android_webview/AwContentsClientBridge.java

Index: android_webview/java/src/org/chromium/android_webview/AwContentsClientBridge.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwContentsClientBridge.java b/android_webview/java/src/org/chromium/android_webview/AwContentsClientBridge.java
index a294913efc1270ead695e6a680faae6726f85b01..b98ba498b08e6fb8b6083ec4a614e43efcae1426 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContentsClientBridge.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContentsClientBridge.java
@@ -7,6 +7,7 @@ package org.chromium.android_webview;
 import android.content.Context;
 import android.net.http.SslCertificate;
 import android.net.http.SslError;
+import android.os.Handler;
 import android.util.Log;
 import android.webkit.ValueCallback;
 
@@ -249,9 +250,18 @@ public class AwContentsClientBridge {
     }
 
     @CalledByNative
-    private void handleJsBeforeUnload(String url, String message, int id) {
-        JsResultHandler handler = new JsResultHandler(this, id);
-        mClient.handleJsBeforeUnload(url, message, handler);
+    private void handleJsBeforeUnload(final String url, final String message, final int id) {
+        // Post the application callback back to the current thread to ensure the application
+        // callback is executed without any native code on the stack. This so that any exception
+        // thrown by the application callback won't have to be propagated through a native call
+        // stack.
+        new Handler().post(new Runnable() {
+            @Override
+            public void run() {
+                JsResultHandler handler = new JsResultHandler(AwContentsClientBridge.this, id);
+                mClient.handleJsBeforeUnload(url, message, handler);
+            }
+        });
     }
 
     @CalledByNative