[Metrics] Make MetricsStateManager take a callback param to check if UMA is enabled.

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 41c2425e33ef3f482ee1072fddf715cc36b67163..cd8c19e23538dd4f6cb635331f1c9b24bf8da13d 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -519,12 +519,6 @@ 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";