[Android] Fix spellcheck JNI crash when a tab is closed.

components/spellcheck/browser/spellchecker_session_bridge_android.cc

Index: components/spellcheck/browser/spellchecker_session_bridge_android.cc
diff --git a/components/spellcheck/browser/spellchecker_session_bridge_android.cc b/components/spellcheck/browser/spellchecker_session_bridge_android.cc
index a34425de098444ed442fa300d9765559c830c7e4..e935a9a87f4377d5cfae3fdec81da68975b1143f 100644
--- a/components/spellcheck/browser/spellchecker_session_bridge_android.cc
+++ b/components/spellcheck/browser/spellchecker_session_bridge_android.cc
@@ -11,6 +11,7 @@
 #include "base/android/jni_string.h"
 #include "components/spellcheck/common/spellcheck_messages.h"
 #include "components/spellcheck/common/spellcheck_result.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
 #include "jni/SpellCheckerSessionBridge_jni.h"
 
@@ -20,7 +21,16 @@ SpellCheckerSessionBridge::SpellCheckerSessionBridge(int render_process_id)
     : render_process_id_(render_process_id),
       java_object_initialization_failed_(false) {}
 
-SpellCheckerSessionBridge::~SpellCheckerSessionBridge() {}
+SpellCheckerSessionBridge::~SpellCheckerSessionBridge() {
+  // Needs to be destroyed on the same thread as the RequestTextCheck and
+  // ProcessSpellCheckResults are executed, which is the UI thread.
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  if (!java_object_.is_null()) {
+    Java_SpellCheckerSessionBridge_disconnect(
+        base::android::AttachCurrentThread(), java_object_);
+  }
+}
 
 // static
 bool SpellCheckerSessionBridge::RegisterJNI(JNIEnv* env) {