Provide a method to remove inserted style sheet

third_party/WebKit/public/web/WebDocument.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 102 matching lines @@
 
   // Gets the accessibility object for this document.
   BLINK_EXPORT WebAXObject AccessibilityObject() const;
 
   // Gets the accessibility object for an object on this page by ID.
   BLINK_EXPORT WebAXObject AccessibilityObjectFromID(int ax_id) const;
 
   // Gets the accessibility object that has focus.
   BLINK_EXPORT WebAXObject FocusedAccessibilityObject() const;
 
-  // Inserts the given CSS source code as a stylesheet in the document.
-  BLINK_EXPORT void InsertStyleSheet(const WebString& source_code);
+  // Inserts the given CSS source code as a stylesheet in the document, and
+  // return its id.
+  BLINK_EXPORT int InsertStyleSheet(const WebString& source_code);

[rune, 2017/05/16 09:00:59]

Could you use a typedef with a suitable id type name instead?

[limasdf, 2017/05/18 12:32:53]

Done.

+
+  // Removes the CSS which was previously inserted by a call to
+  // InsertStyleSheet(). Returns true on success. False means that there's no
+  // corresponding stylesheet.
+  BLINK_EXPORT bool RemoveInsertedStyleSheet(int id);

[rune, 2017/05/16 09:00:59]

Is a return value necessary here?

[limasdf, 2017/05/18 12:32:53]

I was thinking the extension api should return an error message when the user
inserts wrong id.
But it could be done by holding id from extension side. 
So, bool -> void (done).

[rune, 2017/05/16 09:00:59]

These API methods should have a unit test.

[limasdf, 2017/05/18 12:32:53]

Done.

   // Arranges to call WebFrameClient::didMatchCSS(frame(), ...) when one of
   // the selectors matches or stops matching an element in this document.
   // Each call to this method overrides any previous calls.
   BLINK_EXPORT void WatchCSSSelectors(const WebVector<WebString>& selectors);
 
   BLINK_EXPORT WebVector<WebDraggableRegion> DraggableRegions() const;
 
   BLINK_EXPORT v8::Local<v8::Value> RegisterEmbedderCustomElement(
       const WebString& name,
       v8::Local<v8::Value> options,
       WebExceptionCode&);
 
   BLINK_EXPORT WebURL ManifestURL() const;
   BLINK_EXPORT bool ManifestUseCredentials() const;
   BLINK_EXPORT WebDistillabilityFeatures DistillabilityFeatures();
 
 #if BLINK_IMPLEMENTATION
   BLINK_EXPORT WebDocument(Document*);
   BLINK_EXPORT WebDocument& operator=(Document*);
   BLINK_EXPORT operator Document*() const;
 #endif
 };
 
 DECLARE_WEB_NODE_TYPE_CASTS(WebDocument);
 
 }  // namespace blink
 
 #endif