[sync] Remove WARN_UNUSED_RESULTS in various test helpers

Adding a bookmark to a model has -obviously- the side effect that
BookmarkModel gets modified, and there is no reason to enforce that
the caller must hold a reference to the created node.

Change-Id: I8d1ba62aa4ae61053a4ba7dea65348904a04b304
Bug: 1150829
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2557639
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Auto-Submit: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Victor Vianna <victorvianna@google.com>
Cr-Commit-Position: refs/heads/master@{#830606}

chrome/browser/sync/test/integration/bookmarks_helper.h

@@ -76,7 +76,7 @@ bookmarks::BookmarkModel* GetVerifierBookmarkModel() WARN_UNUSED_RESULT;
 // profile |profile|. Returns a pointer to the node that was added.
 const bookmarks::BookmarkNode* AddURL(int profile,
                                       const std::string& title,
-                                      const GURL& url) WARN_UNUSED_RESULT;
+                                      const GURL& url);
 
 // Adds a URL with address |url| and title |title| to the bookmark bar of
 // profile |profile| at position |index|. Returns a pointer to the node that
@@ -84,7 +84,7 @@ const bookmarks::BookmarkNode* AddURL(int profile,
 const bookmarks::BookmarkNode* AddURL(int profile,
                                       size_t index,
                                       const std::string& title,
-                                      const GURL& url) WARN_UNUSED_RESULT;
+                                      const GURL& url);
 
 // Adds a URL with address |url| and title |title| under the node |parent| of
 // profile |profile| at position |index|. Returns a pointer to the node that
@@ -93,19 +93,17 @@ const bookmarks::BookmarkNode* AddURL(int profile,
                                       const bookmarks::BookmarkNode* parent,
                                       size_t index,
                                       const std::string& title,
-                                      const GURL& url) WARN_UNUSED_RESULT;
+                                      const GURL& url);
 
 // Adds a folder named |title| to the bookmark bar of profile |profile|.
 // Returns a pointer to the folder that was added.
-const bookmarks::BookmarkNode* AddFolder(int profile, const std::string& title)
-    WARN_UNUSED_RESULT;
+const bookmarks::BookmarkNode* AddFolder(int profile, const std::string& title);
 
 // Adds a folder named |title| to the bookmark bar of profile |profile| at
 // position |index|. Returns a pointer to the folder that was added.
 const bookmarks::BookmarkNode* AddFolder(int profile,
                                          size_t index,
-                                         const std::string& title)
-    WARN_UNUSED_RESULT;
+                                         const std::string& title);
 
 // Adds a folder named |title| to the node |parent| in the bookmark model of
 // profile |profile| at position |index|. Returns a pointer to the node that
@@ -113,8 +111,7 @@ const bookmarks::BookmarkNode* AddFolder(int profile,
 const bookmarks::BookmarkNode* AddFolder(int profile,
                                          const bookmarks::BookmarkNode* parent,
                                          size_t index,
-                                         const std::string& title)
-    WARN_UNUSED_RESULT;
+                                         const std::string& title);
 
 // Changes the title of the node |node| in the bookmark model of profile
 // |profile| to |new_title|.
@@ -154,7 +151,7 @@ void CheckHasNoFavicon(int profile, const GURL& page_url);
 // |profile| to |new_url|. Returns a pointer to the node with the changed url.
 const bookmarks::BookmarkNode* SetURL(int profile,
                                       const bookmarks::BookmarkNode* node,
-                                      const GURL& new_url) WARN_UNUSED_RESULT;
+                                      const GURL& new_url);
 
 // Moves the node |node| in the bookmark model of profile |profile| so it ends
 // up under the node |new_parent| at position |index|.