Use a valid /prefetch argument when launching a process.

The /prefetch:# argument that is currently added to the command line of
processes launched with content::StartSandboxedProcess is ignored by
Windows because # doesn't respect the [1, 8] constraint.

This CL ensures that a valid /prefetch:# argument is used for every
process launch (except when the feature is disabled by the PreRead
field trial).

BUG=577698

Review URL: https://codereview.chromium.org/1612663002

Cr-Commit-Position: refs/heads/master@{#373241}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 2bea1a18..e22de2a 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -162,6 +162,10 @@
     "//components/ssl_errors",
     "//components/startup_metric_utils/browser:lib",
     "//components/startup_metric_utils/browser:message_filter_lib",
+
+    # TODO(fdoray): Remove this once the PreRead field trial has expired.
+    # crbug.com/577698
+    "//components/startup_metric_utils/common",
     "//components/strings",
     "//components/suggestions",
     "//components/sync_bookmarks",