[fuchsia] Fix net tests by deploying configs to new "/test-shared" dir.

Net tests broke because test process' /data directories are now isolated
and can't be used for sharing data out-of-process. The net test launcher
depends on the old behavior for deploying configuration files to test
code.

This CL designates a special path "/data/shared" into which shared
files will be placed. The shared directory will be mounted at
"/test-shared" in the test process' namespace.

The net test launcher & test code are modified to use the new paths.

TBR=mmenke@chromium.org

Bug: 891732
Change-Id: Id94bffe05a3b140ed60e42507cdc8d238677f202
Reviewed-on: https://chromium-review.googlesource.com/c/1259829
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597193}

base/test/launcher/test_launcher.cc

@@ -364,6 +364,21 @@ int LaunchChildTestProcessWithOptions(const CommandLine& command_line,
                                      base::File::FLAG_DELETE_ON_CLOSE))
                       .release()});
 
+  // The test launcher can use a shared data directory for providing tests with
+  // files deployed at runtime. The files are located under the directory
+  // "/data/shared". They will be mounted at "/test-shared" under the child
+  // process' namespace.
+  const base::FilePath kSharedDataSourcePath("/data/shared");
+  const base::FilePath kSharedDataTargetPath("/test-shared");
+  if (base::PathExists(kSharedDataSourcePath)) {
+    zx::handle shared_directory_handle = base::fuchsia::GetHandleFromFile(
+        base::File(kSharedDataSourcePath,
+                   base::File::FLAG_OPEN | base::File::FLAG_READ |
+                       base::File::FLAG_DELETE_ON_CLOSE));
+    new_options.paths_to_transfer.push_back(
+        {kSharedDataTargetPath, shared_directory_handle.release()});
+  }
+
 #endif  // defined(OS_FUCHSIA)
 
 #if defined(OS_LINUX)

build/fuchsia/net_test_server.py

@@ -130,6 +130,7 @@ def SetupTestServer(target, test_concurrency):
   }))
 
   config_file.flush()
-  target.PutFile(config_file.name, '/data/net-test-server-config')
+  target.RunCommand(['mkdir /data/shared'])
+  target.PutFile(config_file.name, '/data/shared/net-test-server-config')
 
   return spawning_server

net/test/spawned_test_server/remote_test_server_config.cc

@@ -29,7 +29,7 @@ base::FilePath GetTestServerConfigFilePath() {
 #if defined(OS_ANDROID)
   base::PathService::Get(base::DIR_ANDROID_EXTERNAL_STORAGE, &dir);
 #elif defined(OS_FUCHSIA)
-  dir = base::FilePath("/data");
+  dir = base::FilePath("/test-shared");
 #else
   base::PathService::Get(base::DIR_TEMP, &dir);
 #endif