Fix Firefox password importing on the Mac.

Use a plugin child process, which doesn't have library validation.
This way, loading the nss3 dylib into the process will work.

Bug: 1111241
Change-Id: I8c9c6c0c77ac345bfb73e1574bccebc0db9dd791
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2404487Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806293}

chrome/browser/importer/external_process_importer_client.cc

@@ -17,6 +17,7 @@
 #include "chrome/grit/generated_resources.h"
 #include "components/strings/grit/components_strings.h"
 #include "content/public/browser/service_process_host.h"
+#include "content/public/common/child_process_host.h"
 #include "ui/base/l10n/l10n_util.h"
 
 ExternalProcessImporterClient::ExternalProcessImporterClient(
@@ -42,6 +43,12 @@ void ExternalProcessImporterClient::Start() {
       profile_import_.BindNewPipeAndPassReceiver(),
       content::ServiceProcessHost::Options()
           .WithDisplayName(IDS_UTILITY_PROCESS_PROFILE_IMPORTER_NAME)
+#if defined(OS_MAC)
+          // Importing from Firefox involves loading a Firefox dylib into the
+          // importer service process. Use the child process that doesn't
+          // enforce library validation so that this will work.
+          .WithChildFlags(content::ChildProcessHost::CHILD_PLUGIN)
+#endif
           .Pass());
   profile_import_.set_disconnect_handler(
       base::BindOnce(&ExternalProcessImporterClient::OnProcessCrashed, this));