[Android] Avoid using ContentViewCore when detaching from RWHVAndroid

content/browser/renderer_host/render_widget_host_view_android.h

Index: content/browser/renderer_host/render_widget_host_view_android.h
diff --git a/content/browser/renderer_host/render_widget_host_view_android.h b/content/browser/renderer_host/render_widget_host_view_android.h
index 462cabde47f61333c9499a8373932be10ecacbee..180e0f0e986040d44a9bfe19ba85652d4fc73ba4 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.h
+++ b/content/browser/renderer_host/render_widget_host_view_android.h
@@ -330,6 +330,13 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
   // ContentViewCoreImpl is our interface to the view system.
   ContentViewCoreImpl* content_view_core_;
 
+  // Cache the WindowAndroid instance exposed by ContentViewCore to avoid
+  // calling into ContentViewCore when it is being detached from the
+  // WebContents during destruction. The WindowAndroid has stronger lifetime
+  // guarantees, and should be safe to use for observer detachment.
+  // This will be non-null iff |content_view_core_| is non-null.
+  ui::WindowAndroid* content_view_core_window_android_;
+
   ImeAdapterAndroid ime_adapter_android_;
 
   // Body background color of the underlying document.