[protector] Support for collapsing multiple changes into a single one.

chrome/browser/protector/protector_service.h

Index: chrome/browser/protector/protector_service.h
diff --git a/chrome/browser/protector/protector_service.h b/chrome/browser/protector/protector_service.h
index 7d0637d3541ac1c56237897615abe9071cfb1ea8..9eb49d6ed1b9b786d8544c73c1c172817fad528b 100644
--- a/chrome/browser/protector/protector_service.h
+++ b/chrome/browser/protector/protector_service.h
@@ -78,8 +78,16 @@ class ProtectorService : public ProfileKeyedService,
     ~Item();
     linked_ptr<BaseSettingChange> change;
     linked_ptr<SettingsChangeGlobalError> error;
+    // When true, this means |change| was merged with another instance and
+    // |error| is in process of being removed from GlobalErrorService.
+    bool is_merging;

[whywhat, 2012/04/06 16:28:32]

Why merging, not merged as in comment?

[Ivan Korotkov, 2012/04/09 14:46:47]

Fixed

+    // Meaningful only when |merged| is true. In that case, true means that the
+    // new merged GlobalError instance will be immediately shown.
+    bool show_when_merged;

[whywhat, 2012/04/06 16:28:32]

This makes three states represented with two booleans.
Maybe use an enum with three constants?

[Ivan Korotkov, 2012/04/09 14:46:47]

Hm, it doesn't look like a tri-state flag to merge into a single enum, I think.

[whywhat, 2012/04/10 09:55:44]

Both booleans above define three states out of possible four as you state above
(show_when_merged is meaningful only when is_merged is true)

[Ivan Korotkov, 2012/04/10 11:19:49]

I meant that, enum would be good if those were 3 distinct states but (single,
merged and merged,needs show) don't look like distinct states, 2 of them are
nearly the same apart from the show bit.

   };
 
+  typedef std::vector<Item> Items;
+
   // Matches Item by |change| field.
   class MatchItemByChange {
    public:
@@ -102,6 +110,10 @@ class ProtectorService : public ProfileKeyedService,
     const SettingsChangeGlobalError* other_;
   };
 
+  // Returns an Item instance whose change can be merged with |change|, if any.

[whywhat, 2012/04/06 16:28:32]

What if there're multiple items that can be merged?

[Ivan Korotkov, 2012/04/09 14:46:47]

Merging strategy is (and should be) transitive so it shouldn't happen :)

+  // Otherwise returns |NULL|.
+  Item* FindItemToMergeWith(const BaseSettingChange* change);
+
   // ProfileKeyedService implementation.
   virtual void Shutdown() OVERRIDE;
 
@@ -115,7 +127,7 @@ class ProtectorService : public ProfileKeyedService,
 
   // Pointers to error bubble controllers and corresponding changes in the order
   // added.
-  std::vector<Item> items_;
+  Items items_;
 
   // Profile which settings we are protecting.
   Profile* profile_;