content: Add command line flag for native GPU memory buffers.

content/common/gpu/client/gpu_memory_buffer_impl_android.cc

Index: content/common/gpu/client/gpu_memory_buffer_impl_android.cc
diff --git a/content/common/gpu/client/gpu_memory_buffer_impl_android.cc b/content/common/gpu/client/gpu_memory_buffer_impl_android.cc
index cc82b06c41d3bd4f8f0d166b316caccd171a0422..93f5558410813a46c3b9cd6b900e504fa50fafcb 100644
--- a/content/common/gpu/client/gpu_memory_buffer_impl_android.cc
+++ b/content/common/gpu/client/gpu_memory_buffer_impl_android.cc
@@ -14,8 +14,8 @@ namespace content {
 void GpuMemoryBufferImpl::GetSupportedTypes(
     std::vector<gfx::GpuMemoryBufferType>* types) {
   const gfx::GpuMemoryBufferType supported_types[] = {
-    gfx::SURFACE_TEXTURE_BUFFER,
-    gfx::SHARED_MEMORY_BUFFER
+    gfx::SHARED_MEMORY_BUFFER,
+    gfx::SURFACE_TEXTURE_BUFFER

[piman, 2014/11/19 02:39:40]

I would prefer having the decision about the types of buffers that are allowed
to be in a single place.

Really, there's only 2 cases:
1- shm only
2- a single platform-specific type, with a fallback to shm

Which really simplifies to whether or not the platform-specific type (if any) is
allowed.

Maybe it's not worth it to have a list of supported types... We only ever pick
the first element, which may be overridden anyway (from the command line).

I think it would be simpler to have a gfx::GpuMemoryBufferType
GpuMemoryBufferImpl::GetPreferredType() on each platform, which returns a single
type (e.g. EMPTY_BUFFER if none), that may be controlled with the command-line
(on mac and android for a staged rollout).

Then no need for the lazy-initialization logic, or generic override logic.

[reveman, 2014/11/20 00:53:02]

I think my other refactor will result in what you're asking for here. Please
review that patch first and I'll rebase this onto that.

   };
   types->assign(supported_types, supported_types + arraysize(supported_types));
 }