res: Embed FPS into icon_installing.png.

We allow vendor-specific icon installing image but have defined private
animation_fps that can't be overridden. This CL changes the image
generator to optionally embed FPS (otherwise use the default value of
20) into the generated image.

For wear devices, they are using individual images instead of the
interlaced one. Change the animation_fps from private to protected so
that it can be customized.

Bug: 26009230
Change-Id: I9fbf64ec717029d4c54f72316f6cb079e8dbfb5e
diff --git a/screen_ui.h b/screen_ui.h
index 8e18864..08a5f44 100644
--- a/screen_ui.h
+++ b/screen_ui.h
@@ -109,6 +109,8 @@
 
     pthread_t progress_thread_;
 
+    // The following two are parsed from the image file
+    // (e.g. '/res/images/icon_installing.png').
     int animation_fps;
     int installing_frames;
 
@@ -135,7 +137,7 @@
     void DrawTextLines(int* y, const char* const* lines);
 
     void LoadBitmap(const char* filename, GRSurface** surface);
-    void LoadBitmapArray(const char* filename, int* frames, GRSurface*** surface);
+    void LoadBitmapArray(const char* filename, int* frames, int* fps, GRSurface*** surface);
     void LoadLocalizedBitmap(const char* filename, GRSurface** surface);
 };