Enable features API for content shell and webview

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index 3bde098d4f0136f2d513b294a69e1662340890e5..4cc947faf2f6ebfa6ffafbaaf9dccc71a9256a5b 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -695,9 +695,12 @@ int BrowserMainLoop::PreCreateThreads() {
     result_code_ = parts_->PreCreateThreads();
   }
 
-  // Initialize an instance of FeatureList. This will be a no-op if an instance
-  // was already set up by the embedder.
-  base::FeatureList::InitializeInstance();
+  // Initialize from command line flags only if we haven't yet.
+  const base::CommandLine* command_line =
+      base::CommandLine::ForCurrentProcess();
+  base::FeatureList::InitializeInstance(
+      command_line->GetSwitchValueASCII(switches::kEnableFeatures),
+      command_line->GetSwitchValueASCII(switches::kDisableFeatures));
 
   // TODO(chrisha): Abstract away this construction mess to a helper function,
   // once MemoryPressureMonitor is made a concrete class.