Don't launch the unsandboxed GPU process for headless chrome mode

DX12/Vulkan info collection is not needed for headless mode. Don't
launch the unsandboxed GPU process, which is only for info collection.

Bug: 1008904
Change-Id: Ibd0a58ab02675752e86282ef91e2b0b87935e256
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1981130Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Maggie Chen <magchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727480}

headless/lib/DEPS

@@ -5,6 +5,7 @@ specific_include_rules = {
   "headless_content_main_delegate.cc": [
     "+cc/base/switches.h",
     "+components/viz/common/switches.h",
+    "+gpu/config/gpu_switches.h",
   ],
   "headless_web_contents_browsertest.cc": [
     "+cc/base/switches.h",

headless/lib/headless_content_main_delegate.cc

@@ -27,6 +27,7 @@
 #include "content/public/browser/browser_main_runner.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/profiling.h"
+#include "gpu/config/gpu_switches.h"
 #include "headless/lib/browser/headless_browser_impl.h"
 #include "headless/lib/browser/headless_content_browser_client.h"
 #include "headless/lib/headless_crash_reporter_client.h"
@@ -228,6 +229,11 @@ bool HeadlessContentMainDelegate::BasicStartupComplete(int* exit_code) {
   // is ready for display (because it isn't displayed to users).
   command_line->AppendSwitch(::switches::kAllowPreCommitInput);
 
+#if defined(OS_WIN)
+  command_line->AppendSwitch(
+      ::switches::kDisableGpuProcessForDX12VulkanInfoCollection);
+#endif
+
   content::Profiling::ProcessStarted();
   return false;
 }