[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..245bc61f3f7ea584a365f52f88212ebd3f510172 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 +21,11 @@ SpellCheckerSessionBridge::SpellCheckerSessionBridge(int render_process_id)
     : render_process_id_(render_process_id),
       java_object_initialization_failed_(false) {}
 
-SpellCheckerSessionBridge::~SpellCheckerSessionBridge() {}
+SpellCheckerSessionBridge::~SpellCheckerSessionBridge() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  // Clean-up java side to avoid any stale JNI callbacks.
+  DisconnectSession();
+}
 
 // static
 bool SpellCheckerSessionBridge::RegisterJNI(JNIEnv* env) {
@@ -101,7 +106,15 @@ void SpellCheckerSessionBridge::ProcessSpellCheckResults(
 }
 
 void SpellCheckerSessionBridge::DisconnectSession() {

[Tobias Sargeant, 2016/09/30 14:13:21]

If there's an active request at this point that we'll no longer receive, do we
need to fire a SpellCheckMsg_RespondTextCheck?

If a reconnect can happen, we should probably also clear active_request_ and
pending_request_ here, especially as active_request_ will never return, and so
no other requests will be sent to the java bridge.

[timvolodine, 2016/09/30 14:46:00]

Don't think we need to send an (empty?) IPC in the disconnect case. This is
similar to the case when no spellchecker is available for some reason.

Yes added clearing of both active and pending requests --> done.

-  java_object_.Reset();
+  // Needs to be executed on the same thread as the RequestTextCheck and
+  // ProcessSpellCheckResults methods, which is the UI thread.
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  if (!java_object_.is_null()) {
+    Java_SpellCheckerSessionBridge_disconnect(
+        base::android::AttachCurrentThread(), java_object_);
+    java_object_.Reset();
+  }
 }
 
 SpellCheckerSessionBridge::SpellingRequest::SpellingRequest(