Fix CommandBuffer vulkan handle leak in ExternalVkImageBacking

ExternalVkImageBacking was calling Initialize() for the command buffer
returned from VulkanCommandPool::CreatePrimaryCommandBuffer(), but
CreatePrimaryCommandBuffer() already calls Initialize(), i.e.
Initialize() was called twice, which means VkCommandBuffer was created
twice, while only second handle was freed in
VulkanCommandBuffer::Destroy(), the other one was leaked.

This change fixes the issue in ExternalVkImageBacking to avoid the
second Initialize() call. Also added a DCHECK() to avoid this problem in
the future.

Bug: 1001296
Change-Id: I043ddd53952a0650db5cd44835f8d4c244a6e722
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1792853
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
Auto-Submit: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Peng Huang <penghuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694879}

gpu/command_buffer/service/external_vk_image_backing.cc

@@ -784,7 +784,7 @@ bool ExternalVkImageBacking::WritePixels(size_t data_size,
   }
 
   auto command_buffer = command_pool_->CreatePrimaryCommandBuffer();
-  CHECK(command_buffer->Initialize());
+  CHECK(command_buffer);
   {
     ScopedSingleUseCommandBufferRecorder recorder(*command_buffer);
     GrVkImageInfo image_info;

gpu/vulkan/vulkan_command_buffer.cc

@@ -114,6 +114,7 @@ bool VulkanCommandBuffer::Initialize() {
       .commandBufferCount = 1,
   };
 
+  DCHECK_EQ(static_cast<VkCommandBuffer>(VK_NULL_HANDLE), command_buffer_);
   result =
       vkAllocateCommandBuffers(device, &command_buffer_info, &command_buffer_);
   if (VK_SUCCESS != result) {