Do not lose secondary gpus and make sure to have an active gpu on multiple gpu configurations

gpu/config/gpu_switches.cc

Index: gpu/config/gpu_switches.cc
diff --git a/gpu/config/gpu_switches.cc b/gpu/config/gpu_switches.cc
index 554582d81aaf4bd2b14a520a4bb86c7f875a19a9..ef98334be7165c93a83bbddf88a1b2788d649e86 100644
--- a/gpu/config/gpu_switches.cc
+++ b/gpu/config/gpu_switches.cc
@@ -22,6 +22,12 @@ const char kGpuTestingVendorId[] = "gpu-testing-vendor-id";
 // Override gpu device id from the GpuInfoCollector.
 const char kGpuTestingDeviceId[] = "gpu-testing-device-id";
 
+// Override secondary gpu vendor ids from the GpuInfoCollector.
+const char kGpuTestingSecondaryVendorIDs[] = "gpu-testing-secondary-vendor-ids";
+
+// Override secondary gpu device ids from the GpuInfoCollector.
+const char kGpuTestingSecondaryDeviceIDs[] = "gpu-testing-secondary-device-ids";
+
 // Override gl vendor from the GpuInfoCollector.
 const char kGpuTestingGLVendor[] = "gpu-testing-gl-vendor";