content: Move type selection logic out of GpuMemoryBufferImpl.

content/common/gpu/client/gpu_memory_buffer_impl.cc

Index: content/common/gpu/client/gpu_memory_buffer_impl.cc
diff --git a/content/common/gpu/client/gpu_memory_buffer_impl.cc b/content/common/gpu/client/gpu_memory_buffer_impl.cc
index 65edde33f1259e49fb1c0fde177646b3f2d3ddff..972ffa65e3a5ae1d7a89d147ac2ff575c32320a4 100644
--- a/content/common/gpu/client/gpu_memory_buffer_impl.cc
+++ b/content/common/gpu/client/gpu_memory_buffer_impl.cc
@@ -4,9 +4,28 @@
 
 #include "content/common/gpu/client/gpu_memory_buffer_impl.h"
 
+#include "base/lazy_instance.h"
+#include "base/logging.h"
 #include "ui/gl/gl_bindings.h"
 
 namespace content {
+namespace {
+
+gfx::GpuMemoryBufferType g_preferred_type = gfx::EMPTY_BUFFER;
+
+struct DefaultPreferredType {
+  DefaultPreferredType() : value(gfx::EMPTY_BUFFER) {
+    std::vector<gfx::GpuMemoryBufferType> supported_types;
+    GpuMemoryBufferImpl::GetSupportedTypes(&supported_types);
+    DCHECK(!supported_types.empty());
+    value = supported_types[0];
+  }
+  gfx::GpuMemoryBufferType value;
+};
+base::LazyInstance<DefaultPreferredType> g_default_preferred_type =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
 
 GpuMemoryBufferImpl::GpuMemoryBufferImpl(gfx::GpuMemoryBufferId id,
                                          const gfx::Size& size,
@@ -25,6 +44,26 @@ GpuMemoryBufferImpl::~GpuMemoryBufferImpl() {
 }
 
 // static
+void GpuMemoryBufferImpl::SetPreferredType(gfx::GpuMemoryBufferType type) {
+  // EMPTY_BUFFER is a reserved value and not a valid preferred type.
+  DCHECK_NE(gfx::EMPTY_BUFFER, type);
+
+  // Make sure this function is only called once before the first call
+  // to GetPreferredType().
+  DCHECK_EQ(gfx::EMPTY_BUFFER, g_preferred_type);
+
+  g_preferred_type = type;
+}
+
+// static
+gfx::GpuMemoryBufferType GpuMemoryBufferImpl::GetPreferredType() {
+  if (g_preferred_type == gfx::EMPTY_BUFFER)
+    g_preferred_type = g_default_preferred_type.Get().value;
+
+  return g_preferred_type;
+}
+
+// static
 GpuMemoryBufferImpl* GpuMemoryBufferImpl::FromClientBuffer(
     ClientBuffer buffer) {
   return reinterpret_cast<GpuMemoryBufferImpl*>(buffer);