Try 2: Completely redo how themes are stored on disk and processed at install time.

chrome/browser/gtk/gtk_theme_provider.h

Index: chrome/browser/gtk/gtk_theme_provider.h
diff --git a/chrome/browser/gtk/gtk_theme_provider.h b/chrome/browser/gtk/gtk_theme_provider.h
index 60d72e74a22695e57bcb85094dab78c25317841f..44fed998b2005e9756de0dfb2e32951a24348355 100644
--- a/chrome/browser/gtk/gtk_theme_provider.h
+++ b/chrome/browser/gtk/gtk_theme_provider.h
@@ -40,6 +40,9 @@ class GtkThemeProvider : public BrowserThemeProvider,
   // Sets that we aren't using the system theme, then calls
   // BrowserThemeProvider's implementation.
   virtual void Init(Profile* profile);
+  virtual SkBitmap* GetBitmapNamed(int id) const;
+  virtual SkColor GetColor(int id) const;
+  virtual bool HasCustomImage(int id) const;
   virtual void SetTheme(Extension* extension);
   virtual void UseDefaultTheme();
   virtual void SetNativeTheme();
@@ -86,24 +89,17 @@ class GtkThemeProvider : public BrowserThemeProvider,
   static GdkPixbuf* GetFolderIcon(bool native);
   static GdkPixbuf* GetDefaultFavicon(bool native);
 
- protected:
-  // Possibly creates a theme specific version of theme_toolbar_default.
-  // (minimally acceptable version right now, which is just a fill of the bg
-  // color; this should instead invoke gtk_draw_box(...) for complex theme
-  // engines.)
-  virtual SkBitmap* LoadThemeBitmap(int id) const;
-
  private:
+  typedef std::map<int, SkColor> ColorMap;
+  typedef std::map<int, color_utils::HSL> TintMap;
+  typedef std::map<int, SkBitmap*> ImageCache;
+
   // Load theme data from preferences, possibly picking colors from GTK.
   virtual void LoadThemePrefs();
 
   // Let all the browser views know that themes have changed.
   virtual void NotifyThemeChanged();
 
-  // If use_gtk_ is true, completely ignores this call. Otherwise passes it to
-  // the superclass.
-  virtual void SaveThemeBitmap(const std::string resource_name, int id) const;
-
   // Additionally frees the CairoCachedSurfaces.
   virtual void FreePlatformCaches();
 
@@ -115,9 +111,10 @@ class GtkThemeProvider : public BrowserThemeProvider,
   void LoadGtkValues();
 
   // Sets the underlying theme colors/tints from a GTK color.
-  void SetThemeColorFromGtk(const char* id, GdkColor* color);
-  void SetThemeTintFromGtk(const char* id, GdkColor* color,
-                           const color_utils::HSL& default_tint);
+  void SetThemeColorFromGtk(int id, GdkColor* color);
+  void SetThemeTintFromGtk(int id, GdkColor* color);
+  void BuildTintedFrameColor(int color_id, int tint_id);
+  void SetTintToExactColor(int id, GdkColor* color);
 
   // Split out from FreePlatformCaches so it can be called in our destructor;
   // FreePlatformCaches() is called from the BrowserThemeProvider's destructor,
@@ -125,6 +122,16 @@ class GtkThemeProvider : public BrowserThemeProvider,
   // points to GtkThemeProvider's version.
   void FreePerDisplaySurfaces();
 
+  // Lazily generates each bitmap used in the gtk theme.
+  SkBitmap* GenerateGtkThemeBitmap(int id) const;
+
+  // Tints IDR_THEME_FRAME based based on |tint_id|. Used during lazy
+  // generation of the gtk theme bitmaps.
+  SkBitmap* GenerateFrameImage(int tint_id) const;
+
+  // Takes the base frame image |base_id| and tints it with |tint_id|.
+  SkBitmap* GenerateTabImage(int base_id) const;
+
   // A notification from the GtkChromeButton GObject destructor that we should
   // remove it from our internal list.
   static void OnDestroyChromeButton(GtkWidget* button,
@@ -142,6 +149,15 @@ class GtkThemeProvider : public BrowserThemeProvider,
   // them of theme changes.
   std::vector<GtkWidget*> chrome_buttons_;
 
+  // Tints and colors calculated by LoadGtkValues() that are given to the
+  // caller while |use_gtk_| is true.
+  ColorMap colors_;
+  TintMap tints_;
+
+  // Image cache of lazily created images, created when requested by
+  // GetBitmapNamed().
+  mutable ImageCache gtk_images_;
+
   // Cairo surfaces for each GdkDisplay.
   typedef std::map<int, CairoCachedSurface*> CairoCachedSurfaceMap;
   typedef std::map<GdkDisplay*, CairoCachedSurfaceMap> PerDisplaySurfaceMap;