win: Register synthetic field trial for clang builds.

chrome/browser/chrome_browser_main.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <set>
@@ skipping 1336 matching lines @@
   TRACE_EVENT0("startup", "ChromeBrowserMainParts::PreBrowserStart");
   for (size_t i = 0; i < chrome_extra_parts_.size(); ++i)
     chrome_extra_parts_[i]->PreBrowserStart();
 
   three_d_observer_.reset(new ThreeDAPIObserver());
 
 #if defined(SYZYASAN)
   SetupSyzyASAN();
 #endif
 
+#if defined(OS_WIN)
+  ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial("ChromeWinClang",
+#if defined(__clang__)
+                                                            "Enabled"
+#else
+                                                            "Disabled"
+#endif
+                                                            );
+#endif
+
 // Start the tab manager here so that we give the most amount of time for the
 // other services to start up before we start adjusting the oom priority.
 #if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX)
   g_browser_process->GetTabManager()->Start();
 #endif
 
   // The RulesetService will make the filtering rules available to renderers
   // immediately after its construction, provided that the rules are already
   // available at no cost in an indexed format. This enables activating
   // subresource filtering, if needed, also for page loads on start-up.
@@ skipping 733 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }