Pass --log-file along to child processes.

mini_installer_tests captures chrome logs via --log-file=foo. While
other logging switches (e.g., --v, --enable-logging) are being properly
passed to child procs, --log-file was not. This resulted in child procs
writing to the default log file rather than the browser's log file, so
their log messages were not included in the test output upon failure.

BUG=907979

Change-Id: I83eab118d2b196a28db1af0c8abaea3b54f0a783
Reviewed-on: https://chromium-review.googlesource.com/c/1386205
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618548}

content/browser/browser_child_process_host_impl.cc

@@ -317,6 +317,7 @@ void BrowserChildProcessHostImpl::LaunchWithoutExtraCommandLineSwitches(
       switches::kDisableLogging,
       switches::kEnableLogging,
       switches::kIPCConnectionTimeout,
+      switches::kLogFile,
       switches::kLoggingLevel,
       switches::kTraceToConsole,
       switches::kV,

content/browser/renderer_host/render_process_host_impl.cc

@@ -3044,6 +3044,7 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     switches::kFullMemoryCrashReport,
     switches::kIPCConnectionTimeout,
     switches::kJavaScriptFlags,
+    switches::kLogFile,
     switches::kLoggingLevel,
     switches::kMaxUntiledLayerWidth,
     switches::kMaxUntiledLayerHeight,