Spawn GPU process from the unsandboxed zygote.

Now that we have an unsandboxed zygote from https://crrev.com/742875 we
can spawn all process types from it. This ensures we use the same binary
as the browser process even when the on disk version changes.

Bug: 22703
Test: All existing tests still pass.
Change-Id: I56ab870ca591d10723b19ccba2d5de4420d99249
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067393Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743371}

content/app/content_main_runner_impl.cc

@@ -451,6 +451,7 @@ struct MainFunction {
 // Returns the exit code of the subprocess.
 int RunZygote(ContentMainDelegate* delegate) {
   static const MainFunction kMainFunctions[] = {
+    {switches::kGpuProcess, GpuMain},
     {switches::kRendererProcess, RendererMain},
     {switches::kUtilityProcess, UtilityMain},
 #if BUILDFLAG(ENABLE_PLUGINS)

content/browser/gpu/gpu_process_host.cc

@@ -312,14 +312,14 @@ class GpuSandboxedProcessLauncherDelegate
  public:
   explicit GpuSandboxedProcessLauncherDelegate(
       const base::CommandLine& cmd_line)
+      :
 #if defined(OS_WIN)
-      : cmd_line_(cmd_line),
-        enable_appcontainer_(true)
+        enable_appcontainer_(true),
 #endif
-  {
+        cmd_line_(cmd_line) {
   }
 
-  ~GpuSandboxedProcessLauncherDelegate() override {}
+  ~GpuSandboxedProcessLauncherDelegate() override = default;
 
 #if defined(OS_WIN)
   bool DisableDefaultPolicy() override { return true; }
@@ -412,13 +412,22 @@ class GpuSandboxedProcessLauncherDelegate
   void DisableAppContainer() { enable_appcontainer_ = false; }
 #endif  // OS_WIN
 
+#if BUILDFLAG(USE_ZYGOTE_HANDLE)
+  service_manager::ZygoteHandle GetZygote() override {
+    if (service_manager::IsUnsandboxedSandboxType(GetSandboxType()))
+      return nullptr;
+
+    // The GPU process needs a specialized sandbox, so fork from the unsandboxed
+    // zygote and then apply the actual sandboxes in the forked process.
+    return service_manager::GetUnsandboxedZygote();
+  }
+#endif  // BUILDFLAG(USE_ZYGOTE_HANDLE)
+
   service_manager::SandboxType GetSandboxType() override {
-#if defined(OS_WIN)
     if (cmd_line_.HasSwitch(service_manager::switches::kDisableGpuSandbox)) {
       DVLOG(1) << "GPU sandbox is disabled";
       return service_manager::SandboxType::kNoSandbox;
     }
-#endif
     return service_manager::SandboxType::kGpu;
   }
 
@@ -436,9 +445,10 @@ class GpuSandboxedProcessLauncherDelegate
     return base::win::IsRunningUnderDesktopName(STRING16_LITERAL("winlogon"));
   }
 
-  base::CommandLine cmd_line_;
   bool enable_appcontainer_;
-#endif  // OS_WIN
+#endif
+
+  base::CommandLine cmd_line_;
 };
 
 #if defined(OS_WIN)

content/gpu/gpu_main.cc

@@ -48,6 +48,7 @@
 #include "gpu/ipc/service/gpu_watchdog_thread.h"
 #include "media/gpu/buildflags.h"
 #include "services/tracing/public/cpp/stack_sampling/tracing_sampler_profiler.h"
+#include "services/tracing/public/cpp/trace_startup.h"
 #include "third_party/angle/src/gpu_info_util/SystemInfo.h"
 #include "ui/events/platform/platform_event_source.h"
 #include "ui/gfx/switches.h"
@@ -397,6 +398,15 @@ int GpuMain(const MainFunctionParams& parameters) {
 
   gpu_process.set_main_thread(child_thread);
 
+#if defined(OS_POSIX) && !defined(OS_ANDROID) && !defined(OS_MACOSX)
+  // Startup tracing is usually enabled earlier, but if we forked from a zygote,
+  // we can only enable it after mojo IPC support is brought up initialized by
+  // GpuChildThread, because the mojo broker has to create the tracing SMB on
+  // our behalf due to the zygote sandbox.
+  if (parameters.zygote_child)
+    tracing::EnableStartupTracingIfNeeded();
+#endif  // OS_POSIX && !OS_ANDROID && !!OS_MACOSX
+
   // Setup tracing sampler profiler as early as possible.
   std::unique_ptr<tracing::TracingSamplerProfiler> tracing_sampler_profiler =
       tracing::TracingSamplerProfiler::CreateOnMainThread();