ozone: Initialize a subsystem only if necessary.

ui/ozone/generate_ozone_platform_list.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Code generator for Ozone platform list.
 
 This script takes as arguments a list of platform names and generates a C++
 source file containing a list of those platforms. Each list entry contains the
 name and a function pointer to the initializer for that platform.
 
 Example Output: ./generate_ozone_platform_list.py --default wayland dri wayland
 
   #include "ui/ozone/ozone_platform_list.h"
 
   namespace ui {
 
-  OzonePlatform* CreateOzonePlatformDri();
-  OzonePlatform* CreateOzonePlatformWayland();
+  OzonePlatform* CreateOzonePlatformDriForUI();
+  OzonePlatform* CreateOzonePlatformDriForGPU();
+  OzonePlatform* CreateOzonePlatformWaylandForUI();
+  OzonePlatform* CreateOzonePlatformWaylandForGPU();
 
   const OzonePlatformListEntry kOzonePlatforms[] = {
-    { "wayland", &CreateOzonePlatformWayland },
-    { "dri", &CreateOzonePlatformDri },
+    { "wayland",
+      &CreateOzonePlatformWaylandForUI,
+      &CreateOzonePlatformWaylandForGPU },
+    { "dri",
+      &CreateOzonePlatformDriForUI,
+      &CreateOzonePlatformDriForGPU },
   };
 
   const int kOzonePlatformCount = 2;
 
   }  // namespace ui
 """
 
 import optparse
 import os
 import collections
@@ skipping 15 matching lines @@
   """Generate static array containing a list of ozone platforms."""
 
   out.write('#include "ui/ozone/ozone_platform_list.h"\n')
   out.write('\n')
 
   out.write('namespace ui {\n')
   out.write('\n')
 
   # Prototypes for platform initializers.
   for platform in platforms:
-    out.write('OzonePlatform* %s();\n' % GetConstructorName(platform))
+    ctor = GetConstructorName(platform)
+    out.write('OzonePlatform* %sForUI();\nOzonePlatform* %sForGPU();\n' % \
+              (ctor, ctor))
   out.write('\n')
 
   # List of platform names and initializers.
   out.write('const OzonePlatformListEntry kOzonePlatforms[] = {\n')
   for platform in platforms:
-    out.write('  { "%s", &%s },\n' % (platform, GetConstructorName(platform)))
+    ctor = GetConstructorName(platform)
+    out.write('  { "%s", &%sForUI, &%sForGPU },\n' % \
+              (platform, ctor, ctor))
   out.write('};\n')
   out.write('\n')
 
   out.write('const int kOzonePlatformCount = %d;\n' % len(platforms))
   out.write('\n')
 
   out.write('}  // namespace ui\n')
 
 
 def main(argv):
@@ skipping 16 matching lines @@
   GeneratePlatformList(out, platforms)
 
   if options.output_file:
     out.close()
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))