Allow loading SwiftShader after sandbox init on Mac

We could blacklist WebGL based on GL version, which is after creating a context.

Right now this will trigger a failure and GPU process will exit and then
relaunch with SwiftShader mode, which pre-load SwiftShader before sandbox init.

So users will not notice, but this GPU process exit and relaunch is less optimal
and unnecessary.

BUG=897914
TEST=manual
R=kerrnel@chromium.org,kbr@chromium.org,sugoi@chromium.org

Change-Id: Idcd018ca1f2e5161002cdae4563462c76316c606
Reviewed-on: https://chromium-review.googlesource.com/c/1297481Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Greg Kerr <kerrnel@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Zhenyao Mo <zmo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602391}

content/test/gpu/gpu_tests/gpu_process_expectations.py

@@ -12,6 +12,3 @@ class GpuProcessExpectations(GpuTestExpectations):
 
     # Seems to have become flaky on Windows recently.
     self.Flaky('GpuProcess_one_extra_workaround', ['win'], bug=700522)
-
-    self.Fail('GpuProcess_feature_status_under_swiftshader',
-        ['mac'], bug=897914)

services/service_manager/sandbox/mac/cdm.sb

@@ -8,7 +8,6 @@
 (allow file-read* (extension "com.apple.app-sandbox.read"))
 
 ; Allow to read framework and CDM resources files for CDM host verification
-(define bundle-version-path "BUNDLE_VERSION_PATH")
 (allow file-read* (subpath (param bundle-version-path)))
 
 ; mach IPC

services/service_manager/sandbox/mac/common.sb

@@ -14,6 +14,7 @@
 (define (param-defined? str) (string? (param str)))
 
 ; Define constants for all of the parameter strings passed in.
+(define bundle-version-path "BUNDLE_VERSION_PATH")
 (define disable-sandbox-denial-logging "DISABLE_SANDBOX_DENIAL_LOGGING")
 (define enable-logging "ENABLE_LOGGING")
 (define homedir-as-literal "USER_HOMEDIR_AS_LITERAL")

services/service_manager/sandbox/mac/gpu.sb

@@ -29,3 +29,6 @@
 
 ; Needed for VideoToolbox usage - https://crbug.com/767037
 (allow mach-lookup (global-name "com.apple.coremedia.videodecoder"))
+
+; Needed for GPU process to fallback to SwiftShader - https://crbug.com/897914
+(allow file-read-data file-read-metadata (subpath (param bundle-version-path)))

services/service_manager/sandbox/mac/sandbox_mac.mm

@@ -242,7 +242,8 @@ bool SandboxMac::Enable(SandboxType sandbox_type) {
   if (!compiler.InsertBooleanParam(kSandboxMacOS1013, macos_1013))
     return false;
 
-  if (sandbox_type == service_manager::SANDBOX_TYPE_CDM) {
+  if (sandbox_type == service_manager::SANDBOX_TYPE_CDM ||
+      sandbox_type == service_manager::SANDBOX_TYPE_GPU) {
     base::FilePath bundle_path = SandboxMac::GetCanonicalPath(
         base::mac::FrameworkBundlePath().DirName());
     if (!compiler.InsertStringParam(kSandboxBundleVersionPath,