Add support for ContentViewCore helpers on Tab

content/browser/android/content_view_core_impl.cc

Index: content/browser/android/content_view_core_impl.cc
diff --git a/content/browser/android/content_view_core_impl.cc b/content/browser/android/content_view_core_impl.cc
index 4cbc111c061ef455bca4c69ed80b63af6bcfb8b6..71225b7cd0b10846186ccf2398f896907d25634f 100644
--- a/content/browser/android/content_view_core_impl.cc
+++ b/content/browser/android/content_view_core_impl.cc
@@ -256,6 +256,8 @@ ContentViewCoreImpl::ContentViewCoreImpl(
 }
 
 ContentViewCoreImpl::~ContentViewCoreImpl() {
+  root_layer_->RemoveFromParent();
+
   JNIEnv* env = base::android::AttachCurrentThread();
   ScopedJavaLocalRef<jobject> j_obj = java_ref_.get(env);
   java_ref_.reset();
@@ -1303,6 +1305,12 @@ void ContentViewCoreImpl::SetBackgroundOpaque(JNIEnv* env, jobject jobj,
   }
 }
 
+void ContentViewCoreImpl::SetDrawsContent(JNIEnv* env,
+                                          jobject jobj,
+                                          jboolean draws) {
+  GetLayer()->SetHideLayerAndSubtree(!draws);
+}
+
 void ContentViewCoreImpl::RequestTextSurroundingSelection(
     int max_length,
     const base::Callback<