More reliable check for whether EGLSyncControlVSyncProvider should be instantiated.

ui/gl/sync_control_vsync_provider.h

Index: ui/gl/sync_control_vsync_provider.h
diff --git a/ui/gl/sync_control_vsync_provider.h b/ui/gl/sync_control_vsync_provider.h
index 9e196538e03d3109ab867e44f1fef69040f98895..4ef76840b4e833c5669f7d9180bb773d8f06189d 100644
--- a/ui/gl/sync_control_vsync_provider.h
+++ b/ui/gl/sync_control_vsync_provider.h
@@ -23,6 +23,14 @@ class SyncControlVSyncProvider : public gfx::VSyncProvider {
 
   void GetVSyncParameters(const UpdateVSyncCallback& callback) override;
 
+  static constexpr bool IsSupported() {
+#if defined(OS_LINUX)
+    return true;
+#else
+    return false;
+#endif  // defined(OS_LINUX)
+  }
+
  protected:
   virtual bool GetSyncValues(int64_t* system_time,
                              int64_t* media_stream_counter,