Reorganize GUIDs for GPU memory buffers

ui/gfx/gpu_memory_buffer.cc

Index: ui/gfx/gpu_memory_buffer.cc
diff --git a/ui/gfx/gpu_memory_buffer.cc b/ui/gfx/gpu_memory_buffer.cc
index a7655d48ab7c108fea991d60105aec8c79a06e24..b3fb671b1e28184b92e6bedeca5771596c33b095 100644
--- a/ui/gfx/gpu_memory_buffer.cc
+++ b/ui/gfx/gpu_memory_buffer.cc
@@ -4,6 +4,9 @@
 
 #include "ui/gfx/gpu_memory_buffer.h"
 
+#include "ui/gfx/generic_shared_memory_id.h"
+#include "ui/gfx/gpu_memory_buffer_tracing.h"
+
 namespace gfx {
 
 GpuMemoryBufferHandle::GpuMemoryBufferHandle()
@@ -48,4 +51,11 @@ GpuMemoryBufferHandle CloneHandleForIPC(
   return gfx::GpuMemoryBufferHandle();
 }
 
+base::trace_event::MemoryAllocatorDumpGuid
+GpuMemoryBufferHandle::GetGUIDForTracing(uint64_t tracing_process_id) {
+  if (type == gfx::SHARED_MEMORY_BUFFER)

[reveman, 2017/04/17 13:21:06]

not a fan of this special case but should go away if we move GetGUIDForTracing
to the GpuMemoryBuffer API

[ericrk, 2017/04/17 18:10:15]

This special case was added to allow all shared memory allocations use the same
GUID system (whether or not they were GMBs)... This will allow a global shared
memory tracker to alias dumps with shared memory GMBs. My understanding is that
the GetSharedMemoryGUIDForTracing will eventually be replaced with something
that uses shared memory specific data rather than GMB IDs (this is just an
intermediate step).

Maybe we could avoid this, but it seems like it may be more complex? Maybe a
multi-tiered thing (alias GMBs together, then alias shared memory to the GMB in
an extra step in the browser GMB manager?). But I believe this multi-layered
aliasing is currently broken in memory-infra (GPU uses it though, so it will be
fixed eventually).

Let me know if this makes sense.

I agree that this logic probably shouldn't go on the handle though.

[hajimehoshi, 2017/04/18 08:21:58]

Done.

On 2017/04/17 18:10:15, ericrk wrote:
IIUC, when the type is SHARED_MEMORY_BUFFER, the class must be
GpuMemoryBufferImplHandle. The exceptions are subclasses of GpuMemoryBuffer in
tests, but I don't think we need to care them. Thus, defining a virtual function
GetGUIDForTracing to GpuMemoryBuffer and overriding this on
GpuMemoryBufferImplSharedMemory would work.

Right, this is an intermediate step and next I'd need to replace all usages of
GetSharedMemoryGUIDForTracing with one of shared memory tracker.

+    return gfx::GetSharedMemoryGUIDForTracing(tracing_process_id, id);
+  return gfx::GetGenericSharedGpuMemoryGUIDForTracing(tracing_process_id, id);
+}
+
 }  // namespace gfx