gpu: Prefer GL_ARB_sync over GL_NV_fence.

ui/gl/gl_fence.cc

Index: ui/gl/gl_fence.cc
diff --git a/ui/gl/gl_fence.cc b/ui/gl/gl_fence.cc
index 1790f864415f12788297152e9c9645557b834cc5..f44570e2b6042911005dd202a9480322fe76cdf3 100644
--- a/ui/gl/gl_fence.cc
+++ b/ui/gl/gl_fence.cc
@@ -129,10 +129,11 @@ gfx::GLFence* CreateFence(bool flush) {
   if (gfx::g_driver_egl.ext.b_EGL_KHR_fence_sync)
     return new EGLFenceSync(flush);
 #endif
-  if (gfx::g_driver_gl.ext.b_GL_NV_fence)
-    return new GLFenceNVFence(flush);
+  // Prefer ARB_sync which supports server-side wait.
   if (gfx::g_driver_gl.ext.b_GL_ARB_sync)
     return new GLFenceARBSync(flush);
+  if (gfx::g_driver_gl.ext.b_GL_NV_fence)
+    return new GLFenceNVFence(flush);
   return NULL;
 }