Reland "macOS V2 Sandbox: Remove the feature flags."

This is a reland of 5c4908e8

Original change's description:
> macOS V2 Sandbox: Remove the feature flags.
>
> The V2 sandbox is now default for all but the network and GPU processes
> on macOS. This CL deletes the feature flag. A new experiment will be
> introduced for the GPU process. The default case for the sandbox profile
> switch is removed, because previous CHECK() failures were confusing to
> diagnose. All profiles must now be handled explicitly, so Chrome won't
> build if a new profile type isn't handled.
>
> Bug: 749839
> CQ-Depend: 1268671
> Change-Id: I0860d3a5148b0085be6a99dc01c4971602ee5582
> Reviewed-on: https://chromium-review.googlesource.com/c/1269996
> Reviewed-by: Robert Sesek <rsesek@chromium.org>
> Reviewed-by: Mark Pearson <mpearson@chromium.org>
> Reviewed-by: Avi Drissman <avi@chromium.org>
> Commit-Queue: Greg Kerr <kerrnel@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#598128}

CQ-DEPEND=CL:1268671

Bug: 749839
Change-Id: I91544907b640c572823f3aae3e29c0cfa003da51
Reviewed-on: https://chromium-review.googlesource.com/c/1274888Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Greg Kerr <kerrnel@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Greg Kerr <kerrnel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598822}

chrome/browser/about_flags.cc

@@ -2397,9 +2397,6 @@ const FeatureEntry kFeatureEntries[] = {
      SINGLE_VALUE_TYPE(switches::kTrySupportedChannelLayouts)},
 #endif  // OS_WIN
 #if defined(OS_MACOSX)
-    {"mac-v2-sandbox", flag_descriptions::kMacV2SandboxName,
-     flag_descriptions::kMacV2SandboxDescription, kOsMac,
-     FEATURE_VALUE_TYPE(features::kMacV2Sandbox)},
     {"mac-views-task-manager", flag_descriptions::kMacViewsTaskManagerName,
      flag_descriptions::kMacViewsTaskManagerDescription, kOsMac,
      FEATURE_VALUE_TYPE(features::kViewsTaskManager)},

chrome/browser/flag_descriptions.cc

@@ -2980,11 +2980,6 @@ const char kMacRTLDescription[] = "Mirrors the UI for RTL language users";
 const char kMacTouchBarName[] = "Hardware Touch Bar";
 const char kMacTouchBarDescription[] = "Control the use of the Touch Bar.";
 
-const char kMacV2SandboxName[] = "Mac V2 Sandbox";
-const char kMacV2SandboxDescription[] =
-    "Eliminates the unsandboxed warmup phase and sandboxes processes for their "
-    "entire life cycle.";
-
 const char kMacViewsNativeAppWindowsName[] = "Toolkit-Views App Windows.";
 const char kMacViewsNativeAppWindowsDescription[] =
     "Controls whether to use Toolkit-Views based Chrome App windows.";

chrome/browser/flag_descriptions.h

@@ -1800,9 +1800,6 @@ extern const char kMacRTLDescription[];
 extern const char kMacTouchBarName[];
 extern const char kMacTouchBarDescription[];
 
-extern const char kMacV2SandboxName[];
-extern const char kMacV2SandboxDescription[];
-
 extern const char kMacViewsNativeAppWindowsName[];
 extern const char kMacViewsNativeAppWindowsDescription[];
 

content/browser/child_process_launcher_helper_mac.cc

@@ -73,34 +73,8 @@ bool ChildProcessLauncherHelper::BeforeLaunchOnLauncherThread(
       command_line_->HasSwitch(service_manager::switches::kNoSandbox) ||
       service_manager::IsUnsandboxedSandboxType(sandbox_type);
 
-  // TODO(kerrnel): Delete this switch once the V2 sandbox is always enabled.
-  bool use_v2 = base::FeatureList::IsEnabled(features::kMacV2Sandbox);
-
-  switch (sandbox_type) {
-    case service_manager::SANDBOX_TYPE_NO_SANDBOX:
-      break;
-    case service_manager::SANDBOX_TYPE_CDM:
-    case service_manager::SANDBOX_TYPE_PPAPI:
-    case service_manager::SANDBOX_TYPE_RENDERER:
-    case service_manager::SANDBOX_TYPE_UTILITY:
-    case service_manager::SANDBOX_TYPE_NACL_LOADER:
-    case service_manager::SANDBOX_TYPE_PDF_COMPOSITOR:
-    case service_manager::SANDBOX_TYPE_PROFILING:
-      // If the feature experiment is enabled and this process type supports
-      // the v2 sandbox, use it.
-      use_v2 &= true;
-      break;
-    case service_manager::SANDBOX_TYPE_AUDIO:
-      // The audio service only exists with the v2 sandbox.
-      use_v2 |= true;
-      break;
-    default:
-      // This is a 'break' because the V2 sandbox is not enabled for all
-      // processes yet, and so there are sandbox types like NETWORK that
-      // should not be run under the V2 sandbox.
-      use_v2 = false;
-      break;
-  }
+  bool use_v2 =
+      !no_sandbox && (sandbox_type != service_manager::SANDBOX_TYPE_GPU);
 
   if (use_v2 && !no_sandbox) {
     // Generate the profile string.
@@ -133,8 +107,16 @@ bool ChildProcessLauncherHelper::BeforeLaunchOnLauncherThread(
       case service_manager::SANDBOX_TYPE_PROFILING:
         profile += service_manager::kSeatbeltPolicyString_utility;
         break;
-      default:
+      case service_manager::SANDBOX_TYPE_NETWORK:
+        // Put a separate CHECK() for the network sandbox so that crash reports
+        // will show which invalid case was hit.
         CHECK(false);
+        break;
+      case service_manager::SANDBOX_TYPE_INVALID:
+      case service_manager::SANDBOX_TYPE_FIRST_TYPE:
+      case service_manager::SANDBOX_TYPE_AFTER_LAST_TYPE:
+        CHECK(false);
+        break;
     }
 
     // Disable os logging to com.apple.diagnosticd which is a performance

content/public/common/content_features.cc

@@ -656,11 +656,6 @@ const base::Feature kDeviceMonitorMac{"DeviceMonitorMac",
 // Enable IOSurface based screen capturer.
 const base::Feature kIOSurfaceCapturer{"IOSurfaceCapturer",
                                        base::FEATURE_ENABLED_BY_DEFAULT};
-
-// The V2 sandbox on MacOS removes the unsandboed warmup phase and sandboxes the
-// entire life of the process.
-const base::Feature kMacV2Sandbox{"MacV2Sandbox",
-                                  base::FEATURE_ENABLED_BY_DEFAULT};
 #endif  // defined(OS_MACOSX)
 
 enum class VideoCaptureServiceConfiguration {

content/public/common/content_features.h

@@ -159,7 +159,6 @@ CONTENT_EXPORT extern const base::Feature kWebUIPolymer2;
 #if defined(OS_MACOSX)
 CONTENT_EXPORT extern const base::Feature kDeviceMonitorMac;
 CONTENT_EXPORT extern const base::Feature kIOSurfaceCapturer;
-CONTENT_EXPORT extern const base::Feature kMacV2Sandbox;
 #endif  // defined(OS_MACOSX)
 
 // DON'T ADD RANDOM STUFF HERE. Put it in the main section above in

testing/variations/fieldtrial_testing_config.json

@@ -2415,21 +2415,6 @@
             ]
         }
     ],
-    "MacV2Sandbox": [
-        {
-            "platforms": [
-                "mac"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "MacV2Sandbox"
-                    ]
-                }
-            ]
-        }
-    ],
     "MediaFoundationH264Encoding": [
         {
             "platforms": [