ozone: Initialize a subsystem only if necessary.

ui/ozone/generate_ozone_platform_list.py

Index: ui/ozone/generate_ozone_platform_list.py
diff --git a/ui/ozone/generate_ozone_platform_list.py b/ui/ozone/generate_ozone_platform_list.py
index df85a1eab92c136eb5d714d5968c14f53d5c1284..2473dce202f0bf23e24e01259b531cc85d461f3a 100755
--- a/ui/ozone/generate_ozone_platform_list.py
+++ b/ui/ozone/generate_ozone_platform_list.py
@@ -15,12 +15,18 @@ Example Output: ./generate_ozone_platform_list.py --default wayland dri wayland
 
   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;
@@ -56,13 +62,17 @@ def GeneratePlatformList(out, platforms):
 
   # 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')