Don't access destroyed web contents.

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
index 45aa193db6f5fc855533a9a99b0cc52b4f69cdb4..62c634a558f9674ab36f7cf707b6a534a478a350 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
@@ -2099,6 +2099,8 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
     @Nullable public static ChromeActivity fromWebContents(@Nullable WebContents webContents) {
         if (webContents == null) return null;
 
+        if (webContents.isDestroyed()) return null;
+
         WindowAndroid window = webContents.getTopLevelNativeWindow();
         if (window == null) return null;