Let --js-flags work when Harmony is enabled in about:flags (reland)

BUG=

Review URL: https://codereview.chromium.org/606653002

Cr-Commit-Position: refs/heads/master@{#296834}

chrome/browser/about_flags.cc

@@ -806,7 +806,7 @@ const Experiment kExperiments[] = {
     IDS_FLAGS_ENABLE_JAVASCRIPT_HARMONY_NAME,
     IDS_FLAGS_ENABLE_JAVASCRIPT_HARMONY_DESCRIPTION,
     kOsAll,
-    SINGLE_VALUE_TYPE_AND_VALUE(switches::kJavaScriptFlags, "--harmony")
+    SINGLE_VALUE_TYPE(switches::kJavaScriptHarmony)
   },
   {
     "disable-software-rasterizer",

chrome/browser/chrome_content_browser_client.cc

@@ -1364,6 +1364,7 @@ void ChromeContentBrowserClient::AppendExtraCommandLineSwitches(
       switches::kEnableShowModalDialog,
       switches::kEnableStreamlinedHostedApps,
       switches::kEnableWebBasedSignin,
+      switches::kJavaScriptHarmony,
       switches::kMessageLoopHistogrammer,
       switches::kOutOfProcessPdf,
       switches::kPlaybackMode,

chrome/common/chrome_switches.cc

@@ -759,6 +759,9 @@ const char kInstantProcess[]                = "instant-process";
 // enabled.
 const char kInvalidationUseGCMChannel[]     = "invalidation-use-gcm-channel";
 
+// Enables experimental Harmony (ECMAScript 6) features.
+const char kJavaScriptHarmony[]             = "javascript-harmony";
+
 // Specifies the testcase used by the IPC fuzzer.
 const char kIpcFuzzerTestcase[]             = "ipc-fuzzer-testcase";
 

chrome/common/chrome_switches.h

@@ -215,6 +215,7 @@ extern const char kInstallFromWebstore[];
 extern const char kInstantProcess[];
 extern const char kInvalidationUseGCMChannel[];
 extern const char kIpcFuzzerTestcase[];
+extern const char kJavaScriptHarmony[];
 extern const char kKeepAliveForTest[];
 extern const char kKioskMode[];
 extern const char kKioskModePrinting[];

chrome/renderer/chrome_render_process_observer.cc

@@ -264,6 +264,11 @@ ChromeRenderProcessObserver::ChromeRenderProcessObserver(
   if (command_line.HasSwitch(switches::kEnableShowModalDialog))
     WebRuntimeFeatures::enableShowModalDialog(true);
 
+  if (command_line.HasSwitch(switches::kJavaScriptHarmony)) {
+    std::string flag("--harmony");
+    v8::V8::SetFlagsFromString(flag.c_str(), static_cast<int>(flag.size()));
+  }
+
   RenderThread* thread = RenderThread::Get();
   resource_delegate_.reset(new RendererResourceDelegate());
   thread->SetResourceDispatcherDelegate(resource_delegate_.get());

tools/metrics/histograms/histograms.xml

@@ -45422,6 +45422,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1855524566" label="allow-insecure-websocket-from-https-origin"/>
   <int value="1861251313"
       label="enable-message-center-always-scroll-up-upon-notification-removal"/>
+  <int value="1865799183" label="javascript-harmony"/>
   <int value="1900529524" label="disable-touch-drag-drop"/>
   <int value="1906942630" label="enable-easy-unlock"/>
   <int value="1930901873" label="disable-sync-app-list"/>