Implement kCurrentThemeID so we can know what the last theme to be installed ...

chrome/browser/browser_theme_provider.h

Index: chrome/browser/browser_theme_provider.h
===================================================================
--- chrome/browser/browser_theme_provider.h	(revision 22263)
+++ chrome/browser/browser_theme_provider.h	(working copy)
@@ -96,6 +96,8 @@
   static const skia::HSL kDefaultTintFrameIncognitoInactive;
   static const skia::HSL kDefaultTintBackgroundTab;
 
+  static const char* kDefaultThemeID;
+
  public:
   BrowserThemeProvider();
   virtual ~BrowserThemeProvider();
@@ -170,6 +172,10 @@
   // theme is the default theme.
   virtual void SetNativeTheme() { UseDefaultTheme(); }
 
+  // Gets the id of the last installed theme. (The theme may have been further
+  // locally customized.)
+  std::string GetThemeID();
+
   // Convert a bitfield alignment into a string like "top left". Public so that
   // it can be used to generate CSS values. Takes a bitfield of AlignmentMasks.
   static std::string AlignmentToString(int alignment);
@@ -272,6 +278,9 @@
   void SaveTintData();
   void SaveDisplayPropertyData();
 
+  // Save the id of the last theme installed.
+  void SaveThemeID(const std::string& id);
+
   SkColor FindColor(const char* id, SkColor default_color);
 
   // Frees generated images and clears the image cache.