[Metrics] Make MetricsStateManager take a callback param to check if UMA is enabled (take 2)

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index e7230f72e9785ce4b5450fafe6178bff022a14c7..32b09913cf1da39627086ebe97f4b112cf6f3771 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -516,12 +516,6 @@ const char kEnableIPv6[]                    = "enable-ipv6";
 // Enables experimentation with launching ephemeral apps via hyperlinks.
 const char kEnableLinkableEphemeralApps[]   = "enable-linkable-ephemeral-apps";
 
-// Enables metrics recording and reporting in the browser startup sequence, as
-// if this was an official Chrome build where the user allowed metrics
-// reporting. This is used for testing only.
-const char kEnableMetricsReportingForTesting[] =
-    "enable-metrics-reporting-for-testing";
-
 // Runs the Native Client inside the renderer process and enables GPU plugin
 // (internally adds lEnableGpuPlugin to the command line).
 const char kEnableNaCl[]                    = "enable-nacl";