Allow adding an overlay not attached to the tab layer

chrome/browser/android/tab_android.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/tab_android.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
 #include "base/metrics/histogram.h"
@@ skipping 826 matching lines @@
 }
 
 void TabAndroid::DetachOverlayContentViewCore(JNIEnv* env,
                                               jobject obj,
                                               jobject jcontent_view_core) {
   content::ContentViewCore* content_view_core =
       content::ContentViewCore::GetNativeContentViewCore(env,
                                                          jcontent_view_core);
   DCHECK(content_view_core);
 
-  content_view_core->GetLayer()->RemoveFromParent();
+  if (content_view_core->GetLayer()->parent() == content_layer_)
+    content_view_core->GetLayer()->RemoveFromParent();
 }
 
 static void Init(JNIEnv* env, jobject obj) {
   TRACE_EVENT0("native", "TabAndroid::Init");
   // This will automatically bind to the Java object and pass ownership there.
   new TabAndroid(env, obj);
 }
 
 // static
 bool TabAndroid::RegisterTabAndroid(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 static void RecordStartupToCommitUma(JNIEnv* env, jclass jcaller) {
   // Currently it takes about 2000ms to commit a navigation if the measurement
   // begins very early in the browser start. How many buckets (b) are needed to
   // explore the _typical_ values with granularity 100ms and a maximum duration
   // of 1 minute?
   //   s^{n+1} / s^{n} = 2100 / 2000
   //   s = 1.05
   //   s^b = 60000
   //   b = ln(60000) / ln(1.05) ~= 225
   UMA_HISTOGRAM_CUSTOM_TIMES("Startup.FirstCommitNavigationTime",
       base::Time::Now() - chrome::android::GetMainEntryPointTime(),
       base::TimeDelta::FromMilliseconds(1),
       base::TimeDelta::FromMinutes(1),
       225);
 }