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 <[email protected]>
Reviewed-by: Alex Gough <[email protected]>
Reviewed-by: Marijn Kruisselbrink <[email protected]>
Auto-Submit: Mark Rowe <[email protected]>
Commit-Queue: Mark Rowe <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1374160}


CrOS-Libchrome-Original-Commit: 3806c10c31140d32997718e7699255fc30c1abc1

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.