Bug 1460509 - part 67: Mark HTMLEditRules::WillIndent() as MOZ_MUST_USE since it may return NS_ERROR_EDITOR_DESTROYED r=m_kato

MozReview-Commit-ID: 3lP4jp2nOQy

--HG--
extra : rebase_source : d59d4d56370266f454b498811cb82d346636e244

editor/libeditor/HTMLEditRules.h

@@ -327,7 +327,15 @@ protected:
                         bool* aCancel, bool* aHandled,
                         const nsAString* aItemType = nullptr);
   nsresult WillRemoveList(bool aOrdered, bool* aCancel, bool* aHandled);
-  nsresult WillIndent(bool* aCancel, bool* aHandled);
+
+  /**
+   * Called before indenting around Selection.  This method actually tries to
+   * indent the contents.
+   *
+   * @param aCancel             Returns true if the operation is canceled.
+   * @param aHandled            Returns true if the edit action is handled.
+   */
+  MOZ_MUST_USE nsresult WillIndent(bool* aCancel, bool* aHandled);
 
   /**
    * Called before indenting around Selection and it's in CSS mode.