Re-land: content: Single process support for native GpuMemoryBuffers.

content/browser/gpu/browser_gpu_channel_host_factory.cc

Index: content/browser/gpu/browser_gpu_channel_host_factory.cc
diff --git a/content/browser/gpu/browser_gpu_channel_host_factory.cc b/content/browser/gpu/browser_gpu_channel_host_factory.cc
index 9edb9677c56abc2b4801d5aa62193d362236b95c..7625449b9468f05598541ffdb3e95b4e81518a09 100644
--- a/content/browser/gpu/browser_gpu_channel_host_factory.cc
+++ b/content/browser/gpu/browser_gpu_channel_host_factory.cc
@@ -244,6 +244,7 @@ void BrowserGpuChannelHostFactory::Terminate() {
 // static
 void BrowserGpuChannelHostFactory::EnableGpuMemoryBufferFactoryUsage(
     gfx::GpuMemoryBuffer::Usage usage) {
+  DCHECK_EQ(g_enabled_gpu_memory_buffer_usages.Get().count(usage), 0u);
   g_enabled_gpu_memory_buffer_usages.Get().insert(usage);
 }