Add a NavigationThrottle to the public content/ interface

content/public/browser/navigation_throttle.h

Index: content/public/browser/navigation_throttle.h
diff --git a/content/public/browser/navigation_throttle.h b/content/public/browser/navigation_throttle.h
new file mode 100644
index 0000000000000000000000000000000000000000..813cf3991721077534cd49a2e0f5c26b93a0b33e
--- /dev/null
+++ b/content/public/browser/navigation_throttle.h
@@ -0,0 +1,43 @@
+// Copyright 2015 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_NAVIGATION_THROTTLE_H_
+#define CONTENT_PUBLIC_BROWSER_NAVIGATION_THROTTLE_H_
+
+#include "content/common/content_export.h"
+
+namespace content {
+class NavigationHandle;
+
+// A NavigationThrottle tracks is used to interact with a navigation on the UI

[carlosk, 2015/08/28 16:40:25]

/is used to interact/and allows interaction/

[clamy, 2015/09/03 15:30:52]

Done.

+// thread.
+class CONTENT_EXPORT NavigationThrottle {
+ public:
+  // This is returned to the navigation handler to allow the navigation to
+  // proceed, or to cancel it.
+  enum ThrottleCheckResult {
+    PROCEED,
+    CANCEL_AND_IGNORE,

[nasko, 2015/08/31 23:25:15]

Why not just "Cancel" instead of "Cancel and Ignore"? What additional meaning
does "And Ignore" bring?

[clamy, 2015/09/03 15:30:52]

This matches the actions in ResourceController. One of the option is
CancelWithErrorCode, which we may introduce as we transition other Throttles.

+  };
+
+  NavigationThrottle(NavigationHandle* navigation_handle);
+  virtual ~NavigationThrottle();
+
+  // Called when a network request is about to be made for this navigation.
+  virtual ThrottleCheckResult WillStartRequest();
+
+  // Called when a server redirect is received by the navigation.
+  virtual ThrottleCheckResult WillRedirectRequest();
+
+  // The NavigationHandle that is tracking the information related to this
+  // navigation.
+  NavigationHandle* navigation_handle() const { return navigation_handle_; }
+
+ private:
+  NavigationHandle* navigation_handle_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_NAVIGATION_THROTTLE_H_