Fix the multi-threaded access to WeakPtr<BrowsingDataRemoverImpl>

chrome/browser/browsing_data/browsing_data_remover_delegate.h

Index: chrome/browser/browsing_data/browsing_data_remover_delegate.h
diff --git a/chrome/browser/browsing_data/browsing_data_remover_delegate.h b/chrome/browser/browsing_data/browsing_data_remover_delegate.h
index 69600a88d4e9f8059ee358c585ce443790a456cb..01941889538d14b95a3f9d4f92287aa276c054d9 100644
--- a/chrome/browser/browsing_data/browsing_data_remover_delegate.h
+++ b/chrome/browser/browsing_data/browsing_data_remover_delegate.h
@@ -23,15 +23,21 @@ class SpecialStoragePolicy;
 
 class BrowsingDataRemoverDelegate {
  public:
+  // Determines whether |origin| matches |origin_type_mask| given
+  // the |special_storage_policy|.
+  typedef base::Callback<bool(int origin_type_mask,
+                              const GURL& origin,
+                              storage::SpecialStoragePolicy* policy)>
+      MaskMatcherFunction;
+
   virtual ~BrowsingDataRemoverDelegate() {}
 
-  // Determines whether |origin| matches |origin_type_mask|
-  // given the |special_storage_policy|. |origin_type_mask| should only contain
-  // embedder-specific datatypes.
-  virtual bool DoesOriginMatchEmbedderMask(
-      int origin_type_mask,
-      const GURL& origin,
-      storage::SpecialStoragePolicy* special_storage_policy) const = 0;
+  // Returns a MaskMatcherFunction to match embedder's origin types.
+  // This MaskMatcherFunction will be called with an |origin_type_mask|
+  // parameter containing ONLY embedder-defined origin types, and must be able
+  // to handle ALL embedder-defined typed. It must be static and support

[Bernhard Bauer, 2017/03/30 10:49:26]

Nit: The callback doesn't have to be static, it's just that that is an easy way
to ensure thread safety.

[msramek, 2017/04/06 12:06:38]

Indeed. I originally wrote that it "must outlive the associated
BrowsingDataRemover", but then I noticed that there is in fact no reference to
BrowsingDataRemover in this interface, so that might be confusing. I think it's
less confusing to have a stronger requirement.

+  // being called on the UI and IO thread.
+  virtual MaskMatcherFunction GetMaskMatcherFunction() const = 0;
 
   // Removes embedder-specific data.
   virtual void RemoveEmbedderData(