Bug 1710958 [Linux] Delay DMABuf initialization when it's really needed, r=jhorak

Differential Revision: https://phabricator.services.mozilla.com/D115480

gfx/thebes/gfxPlatformGtk.cpp

@@ -115,13 +115,12 @@ gfxPlatformGtk::gfxPlatformGtk() {
     }
   }
 
-  InitBackendPrefs(GetBackendPrefs());
-
 #ifdef MOZ_WAYLAND
-  mUseWebGLDmabufBackend =
-      gfxVars::UseDMABuf() && GetDMABufDevice()->IsDMABufWebGLEnabled();
+  mUseWebGLDmabufBackend = true;
 #endif
 
+  InitBackendPrefs(GetBackendPrefs());
+
   gPlatformFTLibrary = Factory::NewFTLibrary();
   MOZ_RELEASE_ASSERT(gPlatformFTLibrary);
   Factory::SetFTLibrary(gPlatformFTLibrary);
@@ -460,6 +459,15 @@ uint32_t gfxPlatformGtk::MaxGenericSubstitions() {
 
 bool gfxPlatformGtk::AccelerateLayersByDefault() { return true; }
 
+#ifdef MOZ_WAYLAND
+bool gfxPlatformGtk::UseDMABufWebGL() {
+  static bool dmabufAvailable = []() {
+    return gfxVars::UseDMABuf() && GetDMABufDevice()->IsDMABufWebGLEnabled();
+  }();
+  return dmabufAvailable && mUseWebGLDmabufBackend;
+}
+#endif
+
 #if defined(MOZ_X11)
 
 static nsTArray<uint8_t> GetDisplayICCProfile(Display* dpy, Window& root) {

gfx/thebes/gfxPlatformGtk.h

@@ -75,7 +75,7 @@ class gfxPlatformGtk final : public gfxPlatform {
 #endif
 
 #ifdef MOZ_WAYLAND
-  bool UseDMABufWebGL() override { return mUseWebGLDmabufBackend; }
+  bool UseDMABufWebGL() override;
   void DisableDMABufWebGL() { mUseWebGLDmabufBackend = false; }
 #endif