[Media Router] Replace --enable-media-router with trivalue switch

We need a way for users to explicitly disable Media Router if it were
enabled by experiment. This is currently not possible since Media Router
uses FeatureSwitch, and --enable-media-router is considered a "legacy"
switch, which means explicit disabling that overrides experiment
value is not supported (because the fallback value is to disable).
Changing to a tri value flag (1, 0, default) will solve this problem
and allow explicit enabling/disabling of MediaRouter overriding
experiment group.

BUG=552144

Review URL: https://codereview.chromium.org/1420423008

Cr-Commit-Position: refs/heads/master@{#358422}

7 files changed, 11 insertions, 9 deletions

diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index bf65db4..720aff7 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1880,11 +1880,12 @@ const FeatureEntry kFeatureEntries[] = {
      ENABLE_DISABLE_VALUE_TYPE(switches::kV8PacMojoOutOfProcess,
                                switches::kDisableOutOfProcessPac)},
 #if defined(ENABLE_MEDIA_ROUTER) && !defined(OS_ANDROID)
-    {"enable-media-router",
+    {"media-router",
      IDS_FLAGS_ENABLE_MEDIA_ROUTER_NAME,
      IDS_FLAGS_ENABLE_MEDIA_ROUTER_DESCRIPTION,
      kOsDesktop,
-     SINGLE_VALUE_TYPE(switches::kEnableMediaRouter)},
+     ENABLE_DISABLE_VALUE_TYPE_AND_VALUE(
+         switches::kMediaRouter, "1", switches::kMediaRouter, "0")},
 #endif  // defined(ENABLE_MEDIA_ROUTER) && !defined(OS_ANDROID)
 // Since Drive Search is not available when app list is disabled, flag guard
 // enable-drive-search-in-chrome-launcher flag.
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index bf78d63..a76cc80 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -436,9 +436,6 @@ const char kEnableMaterialDesignExtensions[] = "enable-md-extensions";
 // Enables the Material Design policy page at chrome://md-policy.
 const char kEnableMaterialDesignPolicyPage[]  = "enable-md-policy-page";
 
-// Enables Media Router.
-const char kEnableMediaRouter[]             = "enable-media-router";
-
 // Runs the Native Client inside the renderer process and enables GPU plugin
 // (internally adds lEnableGpuPlugin to the command line).
 const char kEnableNaCl[]                    = "enable-nacl";
@@ -720,6 +717,9 @@ const char kMarkNonSecureAsNonSecure[]      = "non-secure";
 // Forces the maximum disk space to be used by the media cache, in bytes.
 const char kMediaCacheSize[]                = "media-cache-size";
 
+// Enables Media Router.
+const char kMediaRouter[]                   = "media-router";
+
 // Enables histograming of tasks served by MessageLoop. See
 // about:histograms/Loop for results, which show frequency of messages on each
 // thread, including APC count, object signalling count, etc.
diff --git a/chrome/common/chrome_switches.h b/chrome/common/chrome_switches.h
index 59d930ab..bb2ccde 100644
--- a/chrome/common/chrome_switches.h
+++ b/chrome/common/chrome_switches.h
@@ -125,7 +125,6 @@ extern const char kEnableFastUnload[];
 extern const char kEnableMaterialDesignDownloads[];
 extern const char kEnableMaterialDesignExtensions[];
 extern const char kEnableMaterialDesignPolicyPage[];
-extern const char kEnableMediaRouter[];
 extern const char kEnableNaCl[];
 extern const char kEnableNavigationTracing[];
 extern const char kEnableNetBenchmarking[];
@@ -202,6 +201,7 @@ extern const char kMarkNonSecureAs[];
 extern const char kMarkNonSecureAsNeutral[];
 extern const char kMarkNonSecureAsNonSecure[];
 extern const char kMediaCacheSize[];
+extern const char kMediaRouter[];
 extern const char kMessageLoopHistogrammer[];
 extern const char kMetricsRecordingOnly[];
 extern const char kMonitoringDestinationID[];
diff --git a/chrome/test/data/webui/media_router/media_router_elements_browsertest.js b/chrome/test/data/webui/media_router/media_router_elements_browsertest.js
index 4672ed4..799315e 100644
--- a/chrome/test/data/webui/media_router/media_router_elements_browsertest.js
+++ b/chrome/test/data/webui/media_router/media_router_elements_browsertest.js
@@ -25,7 +25,7 @@ MediaRouterElementsBrowserTest.prototype = {
   browsePreload: 'chrome://media-router/',
 
   commandLineSwitches: [{
-    switchName: 'enable-media-router',
+    switchName: 'media-router', switchValue: '1'
   }],
 
   // List tests for individual elements.
diff --git a/chrome/test/media_router/media_router_e2e_browsertest.cc b/chrome/test/media_router/media_router_e2e_browsertest.cc
index 465030f..256f26d90 100644
--- a/chrome/test/media_router/media_router_e2e_browsertest.cc
+++ b/chrome/test/media_router/media_router_e2e_browsertest.cc
@@ -29,7 +29,7 @@
 //   --enable-logging=stderr
 //   --whitelisted-extension-id=enhhojjnijigcajfphajepfemndkmdlo
 //   --ui-test-action-timeout=200000
-//   --enable-media-router
+//   --media-router=1
 
 namespace {
 // Command line argument to specify receiver,
diff --git a/extensions/common/feature_switch.cc b/extensions/common/feature_switch.cc
index a8e1d82..81d4347 100644
--- a/extensions/common/feature_switch.cc
+++ b/extensions/common/feature_switch.cc
@@ -48,7 +48,7 @@ class CommonSwitches {
                                    FeatureSwitch::DEFAULT_DISABLED),
         trace_app_source(switches::kTraceAppSource,
                          FeatureSwitch::DEFAULT_ENABLED),
-        // The switch enable-media-router is defined in
+        // The switch media-router is defined in
         // chrome/common/chrome_switches.cc, but we can't depend on chrome here.
         media_router("media-router",
                      kEnableMediaRouterExperiment,
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 4ee71d1..c037404 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -65505,6 +65505,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="-641719457" label="disable-compositor-touch-hit-testing"/>
   <int value="-631740127" label="inert-visual-viewport"/>
   <int value="-622685174" label="enable-pdf-material-ui"/>
+  <int value="-617452890" label="media-router"/>
   <int value="-610411643" label="enable-printer-app-search"/>
   <int value="-604814313" label="enable-pinch"/>
   <int value="-601384286" label="disable-contextual-search"/>