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

chrome/browser/protector/base_setting_change.h

Index: chrome/browser/protector/base_setting_change.h
diff --git a/chrome/browser/protector/base_setting_change.h b/chrome/browser/protector/base_setting_change.h
index 42c52ad7f3c321a0a0a4758e00ad13635b369f63..32ca46fd063c62401c0d83d5ce05788ef95924ac 100644
--- a/chrome/browser/protector/base_setting_change.h
+++ b/chrome/browser/protector/base_setting_change.h
@@ -7,7 +7,7 @@
 #pragma once
 
 #include <string>
-#include <vector>
+#include <utility>
 
 #include "base/basictypes.h"
 #include "base/string16.h"
@@ -20,12 +20,34 @@ struct SessionStartupPref;
 
 namespace protector {
 
+class CompositeSettingsChange;
+
 // Base class for setting change tracked by Protector.
 class BaseSettingChange {
  public:
+  // Pair consisting of a display name representing either new or backup setting
+  // and priority for it. Priority is used for composite changes, consisting
+  // of multiple BaseSettingChange instances - the display name with the highest
+  // priority is used.
+  typedef std::pair<size_t, string16> DisplayName;
+
+  // Default priority value.
+  static const size_t kDefaultNamePriority;
+
   BaseSettingChange();
   virtual ~BaseSettingChange();
 
+  // Merges |this| with |other| and returns a CompositeSettingsChange instance.
+  // Returned instance takes ownership of |other|.
+  // Init should not be called for the returned instance.
+  // |this| may be another CompositeSettingsChange, in which case |other| is
+  // simply added to it and |this| is returned. |other| cannot be
+  // CompositeSettingsChange.
+  virtual CompositeSettingsChange* MergeWith(BaseSettingChange* other);
+
+  // Returns true if |this| is a result of merging some changes with |other|.
+  virtual bool Contains(const BaseSettingChange* other) const;
+
   // Applies initial actions to the setting if needed. Must be called before
   // any other calls are made, including text getters.
   // Returns true if initialization was successful.
@@ -66,6 +88,20 @@ class BaseSettingChange {
   // Returns text for the button to discard the change with |Discard|.
   virtual string16 GetDiscardButtonText() const = 0;
 
+  // Returns the display name and priority for the new setting. If multiple
+  // BaseSettingChange instances are collapsed into MulipleSettingChange
+  // instance, the display name with the highest priority will be used for the
+  // Apply button (Discard button will have a generic caption in that case).
+  // Returns an empty string if there is no specific representaion for new

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

s/representaion/representation
The function returns a pair, it can't return an empty string.

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

Done.

+  // setting value and a generic string should be used.
+  virtual DisplayName GetApplyDisplayName() const;
+
+  // Returns a keyword uniquely identifying new (to be applied) settings.
+  // BaseSettingChange instances with the same keyword may be collapsed into
+  // a single MulipleSettingChange instance. Empty keywords are not considered

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

When do we have an empty keyword? When we don't know that the new setting is?

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

For settings which are not clear how to merge with others, like backup invalid
or startup changed to NTP.

+  // to be equal.
+  virtual std::string GetApplyKeyword() const;
+
  protected:
   // Profile instance we've been associated with by an |Init| call.
   Profile* profile() { return profile_; }