Remove ContainerViewObserver class

content/public/android/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 
 android_aidl("common_aidl") {
   interface_file = "java/src/org/chromium/content/common/common.aidl"
   import_include = "java/src"
@@ skipping 91 matching lines @@
     "java/src/org/chromium/content/browser/ActivityContentVideoViewEmbedder.java",
     "java/src/org/chromium/content/browser/BackgroundSyncNetworkObserver.java",
     "java/src/org/chromium/content/browser/BindingManager.java",
     "java/src/org/chromium/content/browser/BindingManagerImpl.java",
     "java/src/org/chromium/content/browser/BrowserStartupController.java",
     "java/src/org/chromium/content/browser/ChildProcessConnection.java",
     "java/src/org/chromium/content/browser/ChildProcessConnectionImpl.java",
     "java/src/org/chromium/content/browser/ChildProcessConstants.java",
     "java/src/org/chromium/content/browser/ChildProcessCreationParams.java",
     "java/src/org/chromium/content/browser/ChildProcessLauncher.java",
-    "java/src/org/chromium/content/browser/ContainerViewObserver.java",
     "java/src/org/chromium/content/browser/ContentVideoView.java",
     "java/src/org/chromium/content/browser/ContentVideoViewEmbedder.java",
     "java/src/org/chromium/content/browser/ContentView.java",
     "java/src/org/chromium/content/browser/ContentViewClient.java",
     "java/src/org/chromium/content/browser/ContentViewCore.java",
     "java/src/org/chromium/content/browser/ContentViewRenderView.java",
     "java/src/org/chromium/content/browser/ContentViewStatics.java",
     "java/src/org/chromium/content/browser/ContextualSearchClient.java",
     "java/src/org/chromium/content/browser/DeviceSensors.java",
     "java/src/org/chromium/content/browser/DeviceUtils.java",
@@ skipping 313 matching lines @@
     "junit/src/org/chromium/content/browser/input/ThreadedInputConnectionFactoryTest.java",
     "junit/src/org/chromium/content/browser/input/ThreadedInputConnectionTest.java",
     "junit/src/org/chromium/content/browser/BindingManagerImplTest.java",
   ]
   deps = [
     ":content_java",
     "//base:base_java",
     "//base:base_java_test_support",
   ]
 }