Add GenericSharedMemoryId and use w/ GpuMemoryBuffer

ui/gfx/gpu_memory_buffer.h

Index: ui/gfx/gpu_memory_buffer.h
diff --git a/ui/gfx/gpu_memory_buffer.h b/ui/gfx/gpu_memory_buffer.h
index 263a0ef41da40ddd140556c2ccc0d73d51a30afe..6fd088d19b3a0361962a16596a516530b78e2c20 100644
--- a/ui/gfx/gpu_memory_buffer.h
+++ b/ui/gfx/gpu_memory_buffer.h
@@ -5,6 +5,7 @@
 #ifndef UI_GFX_GPU_MEMORY_BUFFER_H_
 #define UI_GFX_GPU_MEMORY_BUFFER_H_
 
+#include "base/memory/generic_shared_memory_id.h"
 #include "base/memory/shared_memory.h"
 #include "base/trace_event/memory_dump_manager.h"
 #include "build/build_config.h"
@@ -24,7 +25,7 @@ enum GpuMemoryBufferType {
   GPU_MEMORY_BUFFER_TYPE_LAST = OZONE_NATIVE_PIXMAP
 };
 
-using GpuMemoryBufferId = int32;
+using GpuMemoryBufferId = base::GenericSharedMemoryId;
 
 struct GFX_EXPORT GpuMemoryBufferHandle {
   GpuMemoryBufferHandle();
@@ -34,10 +35,6 @@ struct GFX_EXPORT GpuMemoryBufferHandle {
   base::SharedMemoryHandle handle;
 };
 
-base::trace_event::MemoryAllocatorDumpGuid GFX_EXPORT
-GetGpuMemoryBufferGUIDForTracing(uint64 tracing_process_id,
-                                 GpuMemoryBufferId buffer_id);

[reveman, 2015/08/10 18:57:32]

Maybe keep this for single process mode where gpu memory buffer implementations
might not be backed by some type of shared memory. e.g. PBO backed GMBs.

[ericrk, 2015/08/10 21:12:14]

Seems like using GenericSharedMemoryId for these in single process mode is the
most straightforward thing rather than special casing this, espeically as
GpuMemoryBufferId == base::GenericSharedMemoryId? Were you just suggesting just
keeping this function/name as a wrapper?

[reveman, 2015/08/10 22:16:13]

Yes, maybe just keeping the function as a wrapper for now as the implementation
might change in the future. While using GenericSharedMemoryId for GMBs not
backed by shared memory is probably fine, using a
"genericsharedmemory-x-process/%" guid might be less appropriate.

[ericrk, 2015/08/11 01:40:07]

sounds good.

-
 // This interface typically correspond to a type of shared memory that is also
 // shared with the GPU. A GPU memory buffer can be written to directly by
 // regular CPU code, but can also be read by the GPU.