Origin policy: fix up feature flag handling

Previously most parts of the code would check if origin policy was enabled, but one part would check if origin policy was enabled *or* if experimental web platform features was enabled. The intention is to have experimental web platform features imply origin policy, which can be done through content_switch_dependent_feature_overrides, and then only having to check if origin policy is enabled.

Bug: 751996
Change-Id: I2da004e77ecc8b72e426b8c62ab944837a92d6a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2063046Reviewed-by: Lily Chen <chlily@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Domenic Denicola <domenic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742862}

content/browser/frame_host/origin_policy_throttle.cc

@@ -34,11 +34,7 @@ void OriginPolicyAddExceptionFor(BrowserContext* browser_context,
 // static
 bool OriginPolicyThrottle::ShouldRequestOriginPolicy(const GURL& url) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  bool origin_policy_enabled =
-      base::FeatureList::IsEnabled(features::kOriginPolicy) ||
-      base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableExperimentalWebPlatformFeatures);
-  if (!origin_policy_enabled)
+  if (!base::FeatureList::IsEnabled(features::kOriginPolicy))
     return false;
 
   if (!url.SchemeIs(url::kHttpsScheme))

content/public/common/content_switch_dependent_feature_overrides.cc

@@ -37,6 +37,9 @@ GetSwitchDependentFeatureOverrides(const base::CommandLine& command_line) {
       {switches::kEnableExperimentalWebPlatformFeatures,
        std::cref(features::kUserAgentClientHint),
        base::FeatureList::OVERRIDE_ENABLE_FEATURE},
+      {switches::kEnableExperimentalWebPlatformFeatures,
+       std::cref(features::kOriginPolicy),
+       base::FeatureList::OVERRIDE_ENABLE_FEATURE},
   };
 
   // TODO(chlily): There are currently a few places where, to check if some