Allow AllocateGpuMemoryBuffer to be called from multiple threads.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 65ecb40bf5e6b6c9979a3ef3da59937896ab2b27..17a3cd9f92869575c2291445a1a3147733690a91 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -406,10 +406,6 @@ void RenderThreadImpl::Init() {
 
   renderer_process_id_ = base::kNullProcessId;
 
-  // AllocateGpuMemoryBuffer must be used exclusively on one thread but
-  // it doesn't have to be the same thread RenderThreadImpl is created on.
-  allocate_gpu_memory_buffer_thread_checker_.DetachFromThread();
-
   TRACE_EVENT_END_ETW("RenderThreadImpl::Init", 0, "");
 }
 
@@ -1074,8 +1070,6 @@ scoped_ptr<gfx::GpuMemoryBuffer> RenderThreadImpl::AllocateGpuMemoryBuffer(
     size_t width,
     size_t height,
     unsigned internalformat) {
-  DCHECK(allocate_gpu_memory_buffer_thread_checker_.CalledOnValidThread());
-
   if (!GpuMemoryBufferImpl::IsFormatValid(internalformat))
     return scoped_ptr<gfx::GpuMemoryBuffer>();