aw: Try to turn crash into java exception

android_webview/java/src/org/chromium/android_webview/AwContents.java

Index: android_webview/java/src/org/chromium/android_webview/AwContents.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwContents.java b/android_webview/java/src/org/chromium/android_webview/AwContents.java
index f4dabeadaadaf7729757bf6c8b320ce54f04f49a..7e71adf90faa4dbb3a39d20e94b9cb67a00b1333 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -1578,6 +1578,10 @@ public class AwContents implements SmartClipProvider,
             }
         }
 
+        // Temporary to generate a Java stack for crbug.com/618807.
+        if (mNativeAwContents == 0) {
+            throw new RuntimeException("Calling load on destroyed webview " + mIsDestroyed);
+        }
         nativeSetExtraHeadersForUrl(
                 mNativeAwContents, params.getUrl(), params.getExtraHttpRequestHeadersString());
         params.setExtraHeaders(new HashMap<String, String>());