Abstract OSMesa from the Layout tests

gpu/ipc/service/gpu_init.cc

Index: gpu/ipc/service/gpu_init.cc
diff --git a/gpu/ipc/service/gpu_init.cc b/gpu/ipc/service/gpu_init.cc
index facd39fcb77598e48e0305b860ffc2cf25625375..8ed804264d88d94cdba97ca0541e1bc0b5921360 100644
--- a/gpu/ipc/service/gpu_init.cc
+++ b/gpu/ipc/service/gpu_init.cc
@@ -224,9 +224,9 @@ bool GpuInit::InitializeAndStartSandbox(const base::CommandLine& command_line) {
   UMA_HISTOGRAM_MEDIUM_TIMES("GPU.InitializeOneOffMediumTime",
                              initialize_one_off_time);
 
-  // OSMesa is expected to run very slowly, so disable the watchdog in that
-  // case.
-  if (gl::GetGLImplementation() == gl::kGLImplementationOSMesaGL) {
+  // Software GL is expected to run slowly, so disable the watchdog
+  // in that case.
+  if (gl::GetGLImplementation() == gl::GetSoftwareGLImplementation()) {
     if (watchdog_thread_)
       watchdog_thread_->Stop();
     watchdog_thread_ = nullptr;