Reland "Use Mojo for communicating with web_app_shortcut_copier"

This is a reland of commit 3806c10c31140d32997718e7699255fc30c1abc1

Don't try to use + to concatenate string literals. Let the C preprocessor concatenate them instead.

Original change's description:
> Use Mojo for communicating with web_app_shortcut_copier
>
> This makes it possible for web_app_shortcut_copier to reliably verify
> the identity of the process that it is performing work on behalf of
> (http://go/peer-process-validation).
>
> `WebAppShortcutCreator` moves away from passing the source and
> destination path to be copied to `web_app_shortcut_copier` via command
> line arguments. Instead a Mojo invitation is passed via the command line
> and a synchronous call is used to request the copy be performed.
>
> `web_app_shortcut_copier` is updated to recover the Mojo endpoint from
> its command line and process the `CopyWebAppShortcut` message. The
> copier exits after a message has been processed.
>
> During initialization, `web_app_shortcut_copier` sets a
> `ProcessRequirement` to prevent anyone other than the browser process
> from establishing a Mojo connection with it. Enforcement of the
> requirement by `MachPortRendezvousClientMac` is currently gated by a
> feature flag. This needs to be enabled by default before the feature
> flag that enables use of `web_app_shortcut_copier` can be enabled.
>
> Bug: 361784552
> Change-Id: I3a9b5128d21223bcd03a4acda2491bb1e42ed896
> Include-Ci-Only-Tests: true
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5924245
> Reviewed-by: Nasko Oskov <nasko@chromium.org>
> Reviewed-by: Alex Gough <ajgo@chromium.org>
> Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
> Auto-Submit: Mark Rowe <markrowe@chromium.org>
> Commit-Queue: Mark Rowe <markrowe@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1374160}

Bug: 361784552
Change-Id: Id6760eb087f3b56e5ad6f0e3fc381e09ef733919
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5968202
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Commit-Queue: Mark Rowe <markrowe@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1374937}


CrOS-Libchrome-Original-Commit: 653850f8272cd92ab8811bc0e3b6fc456887f118

Author: Mark Rowe

mojo/public/cpp/bindings/sync_call_restrictions.h

@@ -48,6 +48,12 @@ class HostFrameSinkManager;
 class HostGpuMemoryBufferManager;
 }  // namespace viz
 
+#if BUILDFLAG(IS_MAC)
+namespace web_app {
+class WebAppShortcutCopierSyncCallHelper;
+}  // namespace web_app
+#endif
+
 namespace mojo {
 class ScopedAllowSyncCallForTesting;
 
@@ -134,6 +140,9 @@ class COMPONENT_EXPORT(MOJO_CPP_BINDINGS) SyncCallRestrictions {
   friend class content::StreamTextureFactory;
 #if BUILDFLAG(IS_WIN)
   friend class content::DCOMPTextureFactory;
+#endif
+#if BUILDFLAG(IS_MAC)
+  friend class web_app::WebAppShortcutCopierSyncCallHelper;
 #endif
   // END ALLOWED USAGE.