Add a switch to prevent logging redirection on chromeos.

This switch will be used by telemetry so all chrome logging goes to
/var/log/chrome/chrome instead of split between this location and
/home/chronos/user/log/chrome, which is in the cryptohome, and sometimes
not collected by autotests.

BUG=chromium:724273
TEST=manual

Review-Url: https://codereview.chromium.org/2893313003
Cr-Commit-Position: refs/heads/master@{#476476}

chrome/browser/chromeos/logging.cc

@@ -9,6 +9,7 @@
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/task_scheduler/post_task.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/logging_chrome.h"
 #include "content/public/browser/browser_thread.h"
 
@@ -51,8 +52,8 @@ void RedirectChromeLogging(const base::CommandLine& command_line) {
     return;
   }
 
-  DCHECK(!chrome_logging_redirected_)
-      << "Attempted to redirect logging when it was already initialized.";
+  if (command_line.HasSwitch(switches::kDisableLoggingRedirect))
+    return;
 
   // Redirect logs to the session log directory, if set.  Otherwise
   // defaults to the profile dir.

chrome/common/chrome_switches.cc

@@ -940,6 +940,9 @@ const char kWebApkServerUrl[] = "webapk-server-url";
 // Custom crosh command.
 const char kCroshCommand[] = "crosh-command";
 
+// Disables logging redirect for testing.
+const char kDisableLoggingRedirect[] = "disable-logging-redirect";
+
 // Disables apps on the login screen. By default, they are allowed and can be
 // installed through policy.
 const char kDisableLoginScreenApps[] = "disable-login-screen-apps";

chrome/common/chrome_switches.h

@@ -273,6 +273,7 @@ extern const char kWebApkServerUrl[];
 
 #if defined(OS_CHROMEOS)
 extern const char kCroshCommand[];
+extern const char kDisableLoggingRedirect[];
 extern const char kDisableLoginScreenApps[];
 extern const char kDisableNativeCups[];
 #endif  // defined(OS_CHROMEOS)