Reorganize GUIDs for GPU memory buffers

cc/raster/staging_buffer_pool.cc

Index: cc/raster/staging_buffer_pool.cc
diff --git a/cc/raster/staging_buffer_pool.cc b/cc/raster/staging_buffer_pool.cc
index 6fa0fe03551d7604e93fdd6a5c89a2f502704a5e..f4556c9ed1f0a4f602296b12511d2b5cb03d27ee 100644
--- a/cc/raster/staging_buffer_pool.cc
+++ b/cc/raster/staging_buffer_pool.cc
@@ -114,8 +114,8 @@ void StagingBuffer::OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd,
   const uint64_t tracing_process_id =
       base::trace_event::MemoryDumpManager::GetInstance()
           ->GetTracingProcessId();
-  MemoryAllocatorDumpGuid shared_buffer_guid =
-      gfx::GetGpuMemoryBufferGUIDForTracing(tracing_process_id, buffer_id);
+  auto shared_buffer_guid =
+      gpu_memory_buffer->GetHandle().GetGUIDForTracing(tracing_process_id);

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

We shouldn't be using the handle for non-IPC things. Can you get the tracing id
from the buffer instead?

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

Done.

   pmd->CreateSharedGlobalAllocatorDump(shared_buffer_guid);
 
   // By creating an edge with a higher |importance| (w.r.t. browser-side dumps)