lacros: Add --lacros-chrome-additional-env for environment variables

For Wayland debugging, it's helpful to add WAYLAND_DEBUG=client to
the lacros environment.

Introduce --lacros-chrome-additional-env to set arbitrary additional
environment variables when launching lacros.

Bug: none
Change-Id: Ie44f4edd80459d606216cab733e99027d42fc986
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2636264Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845052}

chrome/browser/chromeos/crosapi/browser_manager.cc

@@ -310,6 +310,21 @@ void BrowserManager::StartWithLogFile(base::ScopedFD logfd) {
   // This sets the channel for Lacros.
   options.environment["CHROME_VERSION_EXTRA"] = "dev";
 
+  std::string additional_env =
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          chromeos::switches::kLacrosChromeAdditionalEnv);
+  base::StringPairs env_pairs;
+  if (base::SplitStringIntoKeyValuePairsUsingSubstr(additional_env, '=', "####",
+                                                    &env_pairs)) {
+    for (const auto& env_pair : env_pairs) {
+      if (!env_pair.first.empty()) {
+        LOG(WARNING) << "Applying lacros env " << env_pair.first << "="
+                     << env_pair.second;
+        options.environment[env_pair.first] = env_pair.second;
+      }
+    }
+  }
+
   options.kill_on_parent_death = true;
 
   // Paths are UTF-8 safe on Chrome OS.

chromeos/constants/chromeos_switches.cc

@@ -423,6 +423,12 @@ const char kKernelnextRestrictVMs[] = "kernelnext-restrict-vms";
 //   --bar=/tmp/dir name
 const char kLacrosChromeAdditionalArgs[] = "lacros-chrome-additional-args";
 
+// Additional environment variables set for lacros-chrome. The string '####' is
+// used as a delimiter. For example:
+// --lacros-chrome-additional-env=WAYLAND_DEBUG=client####FOO=bar
+// will enable Wayland protocol logging and set FOO=bar.
+const char kLacrosChromeAdditionalEnv[] = "lacros-chrome-additional-env";
+
 // If this switch is set, then ash-chrome will exec the lacros-chrome binary
 // from the indicated path rather than from component updater. Note that the
 // path should be to a directory that contains a binary named 'chrome'.

chromeos/constants/chromeos_switches.h

@@ -164,6 +164,8 @@ extern const char kInstallLogFastUploadForTests[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kKernelnextRestrictVMs[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const char kLacrosChromeAdditionalArgs[];
+COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
+extern const char kLacrosChromeAdditionalEnv[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const char kLacrosChromePath[];
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const char kLacrosMojoSocketForTesting[];