Bug 1840515 - Step 0: Use GeckoArgs for the `-greomni` and `-appomni` flags. r=nika

The `-appomni` flag isn't currently used, but the next patch will bring
it back and change how both flags are processed in child processes.

Differential Revision: https://phabricator.services.mozilla.com/D185330

ipc/glue/GeckoChildProcessHost.cpp

@@ -1263,8 +1263,7 @@ Result<Ok, LaunchError> PosixProcessLauncher::DoSetup() {
       nsAutoCString path;
       nsCOMPtr<nsIFile> file = Omnijar::GetPath(Omnijar::GRE);
       if (file && NS_SUCCEEDED(file->GetNativePath(path))) {
-        mChildArgv.push_back("-greomni");
-        mChildArgv.push_back(path.get());
+        geckoargs::sGREOmni.Put(path.get(), mChildArgv);
       }
     }
 #  endif

toolkit/xre/GeckoArgs.h

@@ -109,6 +109,8 @@ inline void CommandLineArg<uint64_t>::Put(uint64_t aValue,
 static CommandLineArg<const char*> sParentBuildID{"-parentBuildID",
                                                   "parentbuildid"};
 static CommandLineArg<const char*> sAppDir{"-appDir", "appdir"};
+static CommandLineArg<const char*> sGREOmni{"-greomni", "greomni"};
+static CommandLineArg<const char*> sAppOmni{"-appomni", "appomni"};
 static CommandLineArg<const char*> sProfile{"-profile", "profile"};
 
 static CommandLineArg<uint64_t> sJsInitHandle{"-jsInitHandle", "jsinithandle"};