aw: Destroy vulkan GrContext before device queue

GrContext still need device queue in dtor, so we need to delete it
before.

Bug: 1110245, 984955
Change-Id: Ia6c53ade66c8636dc3fcee897c2ff6c286168b15
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2329933Reviewed-by: Peng Huang <penghuang@chromium.org>
Commit-Queue: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793229}

android_webview/browser/gfx/aw_vulkan_context_provider.cc

@@ -92,6 +92,10 @@ AwVulkanContextProvider::AwVulkanContextProvider() {
 AwVulkanContextProvider::~AwVulkanContextProvider() {
   DCHECK_EQ(g_vulkan_context_provider, this);
   g_vulkan_context_provider = nullptr;
+
+  draw_context_.reset();
+  gr_context_.reset();
+
   device_queue_->Destroy();
   device_queue_ = nullptr;
 }