Adds a field trial to control Web API kill switches.

chrome/browser/permissions/permission_context_base.h

Index: chrome/browser/permissions/permission_context_base.h
diff --git a/chrome/browser/permissions/permission_context_base.h b/chrome/browser/permissions/permission_context_base.h
index 440880b957d9a3d30d8f65c321d79fbea0e53921..def8df079512cb22b1f43b285e17fa3e861b5818 100644
--- a/chrome/browser/permissions/permission_context_base.h
+++ b/chrome/browser/permissions/permission_context_base.h
@@ -56,6 +56,12 @@ class PermissionContextBase : public KeyedService {
                         const ContentSettingsType permission_type);
   ~PermissionContextBase() override;
 
+  // A field trial used to enable thw global API kill switch.
+  static const char kApiKillSwitchFieldStudy[];
+
+  // The field trial responsible for rolling out Plugin Power Saver to users.

[mlamouri (slow - plz ping), 2015/10/12 10:51:10]

is the comment correct?

[kcarattini, 2015/10/12 11:05:29]

Nope. Changed

+  static const char kApiKillSwitchFieldParamEnabledValue[];

[mlamouri (slow - plz ping), 2015/10/12 10:51:10]

Could that be in the implementation in the anonymous namespace?

[kcarattini, 2015/10/12 11:05:29]

Doesn't the namespace need to be named to use it in the test?

+
   // The renderer is requesting permission to push messages.
   // When the answer to a permission request has been determined, |callback|
   // should be called with the result.
@@ -79,6 +85,9 @@ class PermissionContextBase : public KeyedService {
   virtual void CancelPermissionRequest(content::WebContents* web_contents,
                                        const PermissionRequestID& id);
 
+  // Whether the kill switch has been enabled for this API.
+  virtual bool IsApiKillSwitchOn() const;
+
  protected:
   // Decide whether the permission should be granted.
   // Calls PermissionDecided if permission can be decided non-interactively,