Add gpu_main_thread_factory.h to expose less of content's guts.

content/public/test/content_test_suite_base.cc

Index: content/public/test/content_test_suite_base.cc
diff --git a/content/public/test/content_test_suite_base.cc b/content/public/test/content_test_suite_base.cc
index c9a2aebb9fd689f6145617568cdb71636482ed59..2c0982838e7ac67385613e0a049ac3f014e2993b 100644
--- a/content/public/test/content_test_suite_base.cc
+++ b/content/public/test/content_test_suite_base.cc
@@ -11,7 +11,7 @@
 #include "base/test/test_suite.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "build/build_config.h"
-#include "content/browser/gpu/gpu_process_host.h"
+#include "content/browser/gpu/gpu_main_thread_factory.h"
 #include "content/browser/renderer_host/render_process_host_impl.h"
 #include "content/browser/utility_process_host_impl.h"
 #include "content/common/url_schemes.h"
@@ -104,7 +104,7 @@ void ContentTestSuiteBase::RegisterInProcessThreads() {
       CreateInProcessUtilityThread);
   RenderProcessHostImpl::RegisterRendererMainThreadFactory(
       CreateInProcessRendererThread);
-  GpuProcessHost::RegisterGpuMainThreadFactory(CreateInProcessGpuThread);
+  content::RegisterGpuMainThreadFactory(CreateInProcessGpuThread);
 }
 
 }  // namespace content