[Cleanup] Move all browsertests to use ScopedFeatureList to modify features

chrome/browser/plugins/flash_permission_browsertest.cc

Index: chrome/browser/plugins/flash_permission_browsertest.cc
diff --git a/chrome/browser/plugins/flash_permission_browsertest.cc b/chrome/browser/plugins/flash_permission_browsertest.cc
index 508190b781429b86275a16e6852ea600640664cd..d43836738892b7d04aaba9ebdc8e6783feffbe45 100644
--- a/chrome/browser/plugins/flash_permission_browsertest.cc
+++ b/chrome/browser/plugins/flash_permission_browsertest.cc
@@ -7,8 +7,10 @@
 #include "base/memory/ptr_util.h"
 #include "base/path_service.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/scoped_feature_list.h"
 #include "chrome/browser/permissions/permissions_browsertest.h"
 #include "chrome/browser/ui/permission_bubble/mock_permission_prompt_factory.h"
+#include "chrome/common/chrome_features.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "components/variations/variations_switches.h"
@@ -47,6 +49,12 @@ class FlashPermissionBrowserTest : public PermissionsBrowserTest {
       : PermissionsBrowserTest("/permissions/flash.html") {}
   ~FlashPermissionBrowserTest() override {}
 
+  void SetUpOnMainThread() override {
+    PermissionsBrowserTest::SetUpOnMainThread();
+    scoped_feature_list_.InitFromCommandLine("PreferHtmlOverPlugins<Study1",
+                                             std::string());

[Ilya Sherman, 2017/06/28 19:56:05]

Hmm, are you sure that this works?  I thought that the test basically runs as
part of SetUpOnMainThread().  Did you mean to override SetUp()?

[chaopeng, 2017/06/30 19:32:36]

I have not test this one yet. But we can not do this in SetUp with field trials.
Same as https://codereview.chromium.org/2929713002/.

+  }
+
   // PermissionsBrowserTest
   void SetUpCommandLine(base::CommandLine* command_line) override {
     PermissionsBrowserTest::SetUpCommandLine(command_line);
@@ -55,8 +63,6 @@ class FlashPermissionBrowserTest : public PermissionsBrowserTest {
 
     // Set a high engagement threshhold so it doesn't interfere with testing the
     // permission.
-    command_line->AppendSwitchASCII(switches::kEnableFeatures,
-                                    "PreferHtmlOverPlugins<Study1");
     command_line->AppendSwitchASCII(switches::kForceFieldTrials,
                                     "Study1/Enabled/");
     command_line->AppendSwitchASCII(
@@ -95,6 +101,9 @@ class FlashPermissionBrowserTest : public PermissionsBrowserTest {
     return RunScriptReturnBool("flashIsEnabled();") ||
            RunScriptReturnBool("flashIsEnabledForPluginWithoutFallback();");
   }
+
+ private:
+  base::test::ScopedFeatureList scoped_feature_list_;
 };
 
 IN_PROC_BROWSER_TEST_F(FlashPermissionBrowserTest,