[lacros] Mojo connection in browser_tests

This CL makes the browser_tests test launcher initiate and establish a
mojo connection with ash-chrome upon launching lacros-chrome.

Bug: 1120582
Change-Id: I2bc42a837804d988575378799044ea1d582972b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2402580Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806835}

content/public/test/browser_test_base.cc

@@ -4,6 +4,7 @@
 
 #include "content/public/test/browser_test_base.h"
 
+#include <fcntl.h>
 #include <stddef.h>
 
 #include <iostream>
@@ -16,6 +17,8 @@
 #include "base/command_line.h"
 #include "base/debug/stack_trace.h"
 #include "base/feature_list.h"
+#include "base/files/file_path.h"
+#include "base/files/scoped_file.h"
 #include "base/i18n/icu_util.h"
 #include "base/location.h"
 #include "base/macros.h"
@@ -33,6 +36,7 @@
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
+#include "build/chromeos_buildflags.h"
 #include "content/browser/browser_main_loop.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/browser/network_service_instance_impl.h"
@@ -62,6 +66,8 @@
 #include "media/base/media_switches.h"
 #include "mojo/public/cpp/bindings/remote.h"
 #include "mojo/public/cpp/bindings/sync_call_restrictions.h"
+#include "mojo/public/cpp/platform/named_platform_channel.h"
+#include "mojo/public/cpp/platform/platform_channel.h"
 #include "net/dns/mock_host_resolver.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"
 #include "services/network/public/cpp/features.h"
@@ -109,6 +115,14 @@
 #include "ui/aura/test/event_generator_delegate_aura.h"  // nogncheck
 #endif
 
+#if BUILDFLAG(IS_LACROS)
+#include "base/files/file_path.h"
+#include "base/files/scoped_file.h"
+#include "mojo/public/cpp/platform/named_platform_channel.h"
+#include "mojo/public/cpp/platform/platform_channel.h"
+#include "mojo/public/cpp/platform/socket_utils_posix.h"
+#endif
+
 namespace content {
 namespace {
 
@@ -338,6 +352,45 @@ void BrowserTestBase::SetUp() {
     use_software_gl = false;
 #endif
 
+#if BUILDFLAG(IS_LACROS)
+  // If the test is running on the lacros environment, a file descriptor needs
+  // to be obtained and used to launch lacros-chrome so that a mojo connection
+  // between lacros-chrome and ash-chrome can be established.
+  // For more details, please see:
+  // //chrome/browser/chromeos/crosapi/test_mojo_connection_manager.h.
+  {
+    // TODO(crbug.com/1127581): Switch to use |kLacrosMojoSocketForTesting| in
+    // //chromeos/constants/chromeos_switches.h.
+    // Please refer to the CL comments for why it can't be done now:
+    // http://crrev.com/c/2402580/2/content/public/test/browser_test_base.cc
+    std::string socket_path =
+        command_line->GetSwitchValueASCII("lacros-mojo-socket-for-testing");
+    if (!socket_path.empty()) {
+      auto channel = mojo::NamedPlatformChannel::ConnectToServer(socket_path);
+      base::ScopedFD socket_fd = channel.TakePlatformHandle().TakeFD();
+
+      // Mark the channel as blocking.
+      int flags = fcntl(socket_fd.get(), F_GETFL);
+      PCHECK(flags != -1);
+      fcntl(socket_fd.get(), F_SETFL, flags & ~O_NONBLOCK);
+
+      uint8_t buf[32];
+      std::vector<base::ScopedFD> descriptors;
+      auto size = mojo::SocketRecvmsg(socket_fd.get(), buf, sizeof(buf),
+                                      &descriptors, true /*block*/);
+      if (size < 0)
+        PLOG(ERROR) << "Error receiving message from the socket";
+      ASSERT_EQ(1, size);
+      EXPECT_EQ(0u, buf[0]);
+      ASSERT_EQ(1u, descriptors.size());
+      // It's OK to release the FD because lacros-chrome's code will consume it.
+      command_line->AppendSwitchASCII(
+          mojo::PlatformChannel::kHandleSwitch,
+          base::NumberToString(descriptors[0].release()));
+    }
+  }
+#endif
+
   if (use_software_gl && !use_software_compositing_)
     command_line->AppendSwitch(switches::kOverrideUseSoftwareGLForTests);
 

content/test/BUILD.gn

@@ -387,6 +387,7 @@ static_library("test_support") {
   deps = [
     ":content_test_mojo_bindings",
     "//base/third_party/dynamic_annotations",
+    "//build:chromeos_buildflags",
     "//cc:test_support",
     "//components/viz/client",
     "//components/viz/host",