Add nullptr check for GpuProcessHost when allocating GpuMemoryBuffer

content/browser/gpu/browser_gpu_memory_buffer_manager.cc

Index: content/browser/gpu/browser_gpu_memory_buffer_manager.cc
diff --git a/content/browser/gpu/browser_gpu_memory_buffer_manager.cc b/content/browser/gpu/browser_gpu_memory_buffer_manager.cc
index 9db43c78485cbadc0969a25a56f7826903bf88fa..ed8a172ab366e9445c768be36903f2a065997fad 100644
--- a/content/browser/gpu/browser_gpu_memory_buffer_manager.cc
+++ b/content/browser/gpu/browser_gpu_memory_buffer_manager.cc
@@ -338,6 +338,13 @@ void BrowserGpuMemoryBufferManager::CreateGpuMemoryBufferOnIO(
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   BufferMap& buffers = clients_[client_id];
 
+  GpuProcessHost* host = GpuProcessHost::Get();
+  if (!host) {
+    DLOG(ERROR) << "Cannot allocate GpuMemoryBuffer with no GpuProcessHost.";
+    callback.Run(gfx::GpuMemoryBufferHandle());
+    return;
+  }
+
   // Note: Handling of cases where the client is removed before the allocation
   // completes is less subtle if we set the buffer type to EMPTY_BUFFER here
   // and verify that this has not changed when creation completes.
@@ -350,7 +357,6 @@ void BrowserGpuMemoryBufferManager::CreateGpuMemoryBufferOnIO(
     return;
   }
 
-  GpuProcessHost* host = GpuProcessHost::Get();
   // Note: Unretained is safe as IO thread is stopped before manager is
   // destroyed.
   host->CreateGpuMemoryBuffer(