Move existing kSitePerProcess checks to a policy-oracle object

content/common/site_isolation_policy.h

Index: content/common/site_isolation_policy.h
diff --git a/content/common/site_isolation_policy.h b/content/common/site_isolation_policy.h
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+++ b/content/common/site_isolation_policy.h
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+// 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_COMMON_SITE_ISOLATION_POLICY_H_
+#define CONTENT_COMMON_SITE_ISOLATION_POLICY_H_
+
+#include "base/basictypes.h"
+#include "content/common/content_export.h"
+#include "url/gurl.h"
+
+namespace content {
+
+// A centralized place for making policy decisions about out-of-process iframes,
+// site isolation, --site-per-process, and related features.
+//
+// This is currently static because all these modes are controlled by command-
+// line flags.
+//
+// These methods can be called from any thread.
+class CONTENT_EXPORT SiteIsolationPolicy {
+ public:
+  // Returns true if the current process model might allow the use of cross-
+  // process iframes. This should typically used to avoid executing codepaths
+  // that only matter for cross-process iframes, to protect the default
+  // behavior.
+  //
+  // Note: Since cross-process frames will soon be possible by default (e.g. for
+  // <iframe src="http://..."> in an extension process), usage should be limited
+  // to temporary stop-gaps.
+  //
+  // Instead of calling this method, prefer to examine object state to see
+  // whether a particular frame happens to have a cross-process relationship
+  // with another, or to consult DoesSiteRequireDedicatedProcess() to see if a
+  // particular site merits protection.
+  static bool AreCrossProcessFramesPossible();
+
+  // Returns true if pages loaded from |url|'s site ought to be handled only by
+  // a renderer process isolated from other sites. If --site-per-process is on
+  // the command line, this is true for all sites.
+  //
+  // Eventually, this function will be made to return true for only some schemes
+  // (e.g. extensions) or a whitelist of sites that we should protect for this
+  // user.
+  //
+  // Although |url| is currently ignored, callers can assume for now that they
+  // can pass a full URL here -- they needn't canonicalize it to a site.
+  static bool DoesSiteRequireDedicatedProcess(const GURL& url);
+
+  // Returns true if navigation and history code should maintain per-frame
+  // navigation entries. This is an in-progress feature related to site
+  // isolation, so the return value is currently tied to --site-per-process.
+  // TODO(creis, avi): Make this the default, and eliminate this.
+  static bool UseSubframeNavigationEntries();
+
+ private:
+  SiteIsolationPolicy();  // Not instantiable.
+
+  DISALLOW_COPY_AND_ASSIGN(SiteIsolationPolicy);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_SITE_ISOLATION_POLICY_H_