Implement CSP check for manifest fetching

Source/core/frame/csp/ContentSecurityPolicy.h

Index: Source/core/frame/csp/ContentSecurityPolicy.h
diff --git a/Source/core/frame/csp/ContentSecurityPolicy.h b/Source/core/frame/csp/ContentSecurityPolicy.h
index 55690b5fa28ea24775458bae413acd2f649878ba..a2aaf590a1a12e8519a8e42fbed7cc6fb2ca8584 100644
--- a/Source/core/frame/csp/ContentSecurityPolicy.h
+++ b/Source/core/frame/csp/ContentSecurityPolicy.h
@@ -75,7 +75,7 @@ public:
     static const char ScriptSrc[];
     static const char StyleSrc[];
 
-    // CSP 1.1 Directives
+    // CSP Level 2 Directives
     static const char BaseURI[];
     static const char ChildSrc[];
     static const char FormAction[];
@@ -84,6 +84,10 @@ public:
     static const char ReflectedXSS[];
     static const char Referrer[];
 
+    // Manifest Directives (to be merged into CSP Level 2)
+    // https://w3c.github.io/manifest/#content-security-policy
+    static const char ManifestSrc[];
+
     enum ReportingStatus {
         SendReport,
         SuppressReport
@@ -127,6 +131,8 @@ public:
     bool allowChildContextFromSource(const KURL&, ReportingStatus = SendReport) const;
     bool allowWorkerContextFromSource(const KURL&, ReportingStatus = SendReport) const;
 
+    bool allowManifestFromSource(const KURL&, ReportingStatus = SendReport) const;
+
     // The nonce and hash allow functions are guaranteed to not have any side
     // effects, including reporting.
     // Nonce/Hash functions check all policies relating to use of a script/style