android: Fix ContentViewCore and RenderWidgetHostViewAndroid lifetime issue

content/browser/android/web_contents_observer_android.cc

Index: content/browser/android/web_contents_observer_android.cc
diff --git a/content/browser/android/web_contents_observer_android.cc b/content/browser/android/web_contents_observer_android.cc
index 235041be67422e2924b9bf106d613693048a5df0..03f1af66e5d24ba37217bddeb27b284293924b2b 100644
--- a/content/browser/android/web_contents_observer_android.cc
+++ b/content/browser/android/web_contents_observer_android.cc
@@ -28,8 +28,10 @@ namespace content {
 WebContentsObserverAndroid::WebContentsObserverAndroid(
     JNIEnv* env,
     jobject obj,
+    ContentViewCore* content_view_core,
     WebContents* web_contents)
     : WebContentsObserver(web_contents),
+      content_view_core_(content_view_core),
       weak_java_observer_(env, obj){
 }
 
@@ -40,7 +42,7 @@ jlong Init(JNIEnv* env, jobject obj, jlong native_content_view_core) {
   ContentViewCore* content_view_core =
       reinterpret_cast<ContentViewCore*>(native_content_view_core);
   WebContentsObserverAndroid* native_observer = new WebContentsObserverAndroid(
-      env, obj, content_view_core->GetWebContents());
+      env, obj, content_view_core, content_view_core->GetWebContents());
   return reinterpret_cast<intptr_t>(native_observer);
 }
 
@@ -50,6 +52,8 @@ void WebContentsObserverAndroid::Destroy(JNIEnv* env, jobject obj) {
 
 void WebContentsObserverAndroid::WebContentsDestroyed(
     WebContents* web_contents) {
+  content_view_core_->OnDetachedFromWebContents(web_contents);
+
   JNIEnv* env = AttachCurrentThread();
   ScopedJavaLocalRef<jobject> obj(weak_java_observer_.get(env));
   if (obj.is_null()) {