[Fuchsia] Fix FilteredServiceDirectory to copy service name from char*.

Previously FilteredServiceDirectory was taking service names as char*
and then retaining that pointer to use it later. This didn't work
correctly when AddService() was called with name that's not stored in a
static buffer. Updated it to take StringPiece and then copy it to
std::string internally.

Change-Id: I382e3929eabb9806f4a74664ed355da886dcc61a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935723Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Auto-Submit: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719417}

base/fuchsia/filtered_service_directory.cc

@@ -20,15 +20,15 @@ FilteredServiceDirectory::FilteredServiceDirectory(
 
 FilteredServiceDirectory::~FilteredServiceDirectory() {}
 
-void FilteredServiceDirectory::AddService(const char* service_name) {
+void FilteredServiceDirectory::AddService(base::StringPiece service_name) {
   outgoing_directory_.AddPublicService(
       std::make_unique<vfs::Service>(
-          [this, service_name](zx::channel channel,
-                               async_dispatcher_t* dispatcher) {
+          [this, service_name = service_name.as_string()](
+              zx::channel channel, async_dispatcher_t* dispatcher) {
             DCHECK_EQ(dispatcher, async_get_default_dispatcher());
             directory_->Connect(service_name, std::move(channel));
           }),
-      service_name);
+      service_name.as_string());
 }
 
 void FilteredServiceDirectory::ConnectClient(

base/fuchsia/filtered_service_directory.h

@@ -14,6 +14,7 @@
 
 #include "base/base_export.h"
 #include "base/macros.h"
+#include "base/strings/string_piece.h"
 
 namespace base {
 namespace fuchsia {
@@ -28,7 +29,7 @@ class BASE_EXPORT FilteredServiceDirectory {
   ~FilteredServiceDirectory();
 
   // Adds the specified service to the list of whitelisted services.
-  void AddService(const char* service_name);
+  void AddService(base::StringPiece service_name);
 
   // Connects a directory client. The directory can be passed to a sandboxed
   // process to be used for /svc namespace.