--- a/dom/security/nsCSPContext.cpp
+++ b/dom/security/nsCSPContext.cpp
@@ -1622,24 +1622,16 @@ NS_IMETHODIMP
 nsCSPContext::Permits(Element* aTriggeringElement,
                       nsICSPEventListener* aCSPEventListener, nsIURI* aURI,
                       CSPDirective aDir, bool aSpecific, bool* outPermits) {
   // Can't perform check without aURI
   if (aURI == nullptr) {
     return NS_ERROR_FAILURE;
   }
 
-  // CSP_SubjectToCSP allow lists some internal schemes but also some
-  // specific content types. Using TYPE_OTHER as a default which will
-  // still allow list all allow listed schemes.
-  if (!CSP_SubjectToCSP(aURI, nsIContentPolicy::TYPE_OTHER)) {
-    *outPermits = true;
-    return NS_OK;
-  }
-
   *outPermits =
       permitsInternal(aDir, aTriggeringElement, aCSPEventListener, aURI,
                       nullptr,        // no original (pre-redirect) URI
                       EmptyString(),  // no nonce
                       false,          // not a preload.
                       aSpecific,
                       true,    // send violation reports
                       true,    // send blocked URI in violation reports

--- a/dom/security/nsCSPService.cpp
+++ b/dom/security/nsCSPService.cpp
@@ -26,16 +26,86 @@ using namespace mozilla;
 static LazyLogModule gCspPRLog("CSP");
 
 CSPService::CSPService() = default;
 
 CSPService::~CSPService() = default;
 
 NS_IMPL_ISUPPORTS(CSPService, nsIContentPolicy, nsIChannelEventSink)
 
+// Helper function to identify protocols and content types not subject to CSP.
+bool subjectToCSP(nsIURI* aURI, nsContentPolicyType aContentType) {
+  nsContentPolicyType contentType =
+      nsContentUtils::InternalContentPolicyTypeToExternal(aContentType);
+
+  // These content types are not subject to CSP content policy checks:
+  // TYPE_CSP_REPORT -- csp can't block csp reports
+  // TYPE_REFRESH    -- never passed to ShouldLoad (see nsIContentPolicy.idl)
+  // TYPE_DOCUMENT   -- used for frame-ancestors
+  if (contentType == nsIContentPolicy::TYPE_CSP_REPORT ||
+      contentType == nsIContentPolicy::TYPE_REFRESH ||
+      contentType == nsIContentPolicy::TYPE_DOCUMENT) {
+    return false;
+  }
+
+  // The three protocols: data:, blob: and filesystem: share the same
+  // protocol flag (URI_IS_LOCAL_RESOURCE) with other protocols,
+  // but those three protocols get special attention in CSP and
+  // are subject to CSP, hence we have to make sure those
+  // protocols are subject to CSP, see:
+  // http://www.w3.org/TR/CSP2/#source-list-guid-matching
+  if (aURI->SchemeIs("data") || aURI->SchemeIs("blob") ||
+      aURI->SchemeIs("filesystem")) {
+    return true;
+  }
+
+  // Finally we have to whitelist "about:" which does not fall into
+  // the category underneath and also "javascript:" which is not
+  // subject to CSP content loading rules.
+  if (aURI->SchemeIs("about") || aURI->SchemeIs("javascript")) {
+    return false;
+  }
+
+  // Please note that it should be possible for websites to
+  // whitelist their own protocol handlers with respect to CSP,
+  // hence we use protocol flags to accomplish that, but we also
+  // want resource:, chrome: and moz-icon to be subject to CSP
+  // (which also use URI_IS_LOCAL_RESOURCE).
+  // Exception to the rule are images, styles, and localization
+  // DTDs using a scheme of resource: or chrome:
+  bool isImgOrStyleOrDTD = contentType == nsIContentPolicy::TYPE_IMAGE ||
+                           contentType == nsIContentPolicy::TYPE_STYLESHEET ||
+                           contentType == nsIContentPolicy::TYPE_DTD;
+  if (aURI->SchemeIs("resource")) {
+    nsAutoCString uriSpec;
+    aURI->GetSpec(uriSpec);
+    // Exempt pdf.js from being subject to a page's CSP.
+    if (StringBeginsWith(uriSpec, NS_LITERAL_CSTRING("resource://pdf.js/"))) {
+      return false;
+    }
+    if (!isImgOrStyleOrDTD) {
+      return true;
+    }
+  }
+  if (aURI->SchemeIs("chrome") && !isImgOrStyleOrDTD) {
+    return true;
+  }
+  if (aURI->SchemeIs("moz-icon")) {
+    return true;
+  }
+  bool match;
+  nsresult rv = NS_URIChainHasFlags(
+      aURI, nsIProtocolHandler::URI_IS_LOCAL_RESOURCE, &match);
+  if (NS_SUCCEEDED(rv) && match) {
+    return false;
+  }
+  // all other protocols are subject To CSP.
+  return true;
+}
+
 /* static */ nsresult CSPService::ConsultCSP(nsIURI* aContentLocation,
                                              nsILoadInfo* aLoadInfo,
                                              const nsACString& aMimeTypeGuess,
                                              int16_t* aDecision) {
   if (!aContentLocation) {
     return NS_ERROR_FAILURE;
   }
 
@@ -55,19 +125,19 @@ NS_IMPL_ISUPPORTS(CSPService, nsIContent
 
   // default decision, CSP can revise it if there's a policy to enforce
   *aDecision = nsIContentPolicy::ACCEPT;
 
   // No need to continue processing if CSP is disabled or if the protocol
   // or type is *not* subject to CSP.
   // Please note, the correct way to opt-out of CSP using a custom
   // protocolHandler is to set one of the nsIProtocolHandler flags
-  // that are whitelistet in CSP_SubjectToCSP()
+  // that are whitelistet in subjectToCSP()
   if (!StaticPrefs::security_csp_enable() ||
-      !CSP_SubjectToCSP(aContentLocation, contentType)) {
+      !subjectToCSP(aContentLocation, contentType)) {
     return NS_OK;
   }
 
   nsAutoString cspNonce;
   rv = aLoadInfo->GetCspNonce(cspNonce);
   NS_ENSURE_SUCCESS(rv, rv);
 
   // 1) Apply speculate CSP for preloads
@@ -236,20 +306,20 @@ nsresult CSPService::ConsultCSPForRedire
       return NS_OK;
     }
   }
 
   // No need to continue processing if CSP is disabled or if the protocol
   // is *not* subject to CSP.
   // Please note, the correct way to opt-out of CSP using a custom
   // protocolHandler is to set one of the nsIProtocolHandler flags
-  // that are whitelistet in CSP_SubjectToCSP()
+  // that are whitelistet in subjectToCSP()
   nsContentPolicyType policyType = aLoadInfo->InternalContentPolicyType();
   if (!StaticPrefs::security_csp_enable() ||
-      !CSP_SubjectToCSP(aNewURI, policyType)) {
+      !subjectToCSP(aNewURI, policyType)) {
     return NS_OK;
   }
 
   nsCOMPtr<nsICSPEventListener> cspEventListener;
   nsresult rv =
       aLoadInfo->GetCspEventListener(getter_AddRefs(cspEventListener));
   MOZ_ALWAYS_SUCCEEDS(rv);
 

--- a/dom/security/nsCSPUtils.cpp
+++ b/dom/security/nsCSPUtils.cpp
@@ -455,85 +455,16 @@ bool permitsScheme(const nsAString& aEnf
   // the error back to the page.
   return (
       (aUpgradeInsecure && !aReportOnly) &&
       ((scheme.EqualsASCII("http") &&
         aEnforcementScheme.EqualsASCII("https")) ||
        (scheme.EqualsASCII("ws") && aEnforcementScheme.EqualsASCII("wss"))));
 }
 
-bool CSP_SubjectToCSP(nsIURI* aURI, nsContentPolicyType aContentType) {
-  nsContentPolicyType contentType =
-      nsContentUtils::InternalContentPolicyTypeToExternal(aContentType);
-
-  // These content types are not subject to CSP content policy checks:
-  // TYPE_CSP_REPORT -- csp can't block csp reports
-  // TYPE_REFRESH    -- never passed to ShouldLoad (see nsIContentPolicy.idl)
-  // TYPE_DOCUMENT   -- used for frame-ancestors
-  if (contentType == nsIContentPolicy::TYPE_CSP_REPORT ||
-      contentType == nsIContentPolicy::TYPE_REFRESH ||
-      contentType == nsIContentPolicy::TYPE_DOCUMENT) {
-    return false;
-  }
-
-  // The three protocols: data:, blob: and filesystem: share the same
-  // protocol flag (URI_IS_LOCAL_RESOURCE) with other protocols,
-  // but those three protocols get special attention in CSP and
-  // are subject to CSP, hence we have to make sure those
-  // protocols are subject to CSP, see:
-  // http://www.w3.org/TR/CSP2/#source-list-guid-matching
-  if (aURI->SchemeIs("data") || aURI->SchemeIs("blob") ||
-      aURI->SchemeIs("filesystem")) {
-    return true;
-  }
-
-  // Finally we have to whitelist "about:" which does not fall into
-  // the category underneath and also "javascript:" which is not
-  // subject to CSP content loading rules.
-  if (aURI->SchemeIs("about") || aURI->SchemeIs("javascript")) {
-    return false;
-  }
-
-  // Please note that it should be possible for websites to
-  // whitelist their own protocol handlers with respect to CSP,
-  // hence we use protocol flags to accomplish that, but we also
-  // want resource:, chrome: and moz-icon to be subject to CSP
-  // (which also use URI_IS_LOCAL_RESOURCE).
-  // Exception to the rule are images, styles, and localization
-  // DTDs using a scheme of resource: or chrome:
-  bool isImgOrStyleOrDTD = contentType == nsIContentPolicy::TYPE_IMAGE ||
-                           contentType == nsIContentPolicy::TYPE_STYLESHEET ||
-                           contentType == nsIContentPolicy::TYPE_DTD;
-  if (aURI->SchemeIs("resource")) {
-    nsAutoCString uriSpec;
-    aURI->GetSpec(uriSpec);
-    // Exempt pdf.js from being subject to a page's CSP.
-    if (StringBeginsWith(uriSpec, NS_LITERAL_CSTRING("resource://pdf.js/"))) {
-      return false;
-    }
-    if (!isImgOrStyleOrDTD) {
-      return true;
-    }
-  }
-  if (aURI->SchemeIs("chrome") && !isImgOrStyleOrDTD) {
-    return true;
-  }
-  if (aURI->SchemeIs("moz-icon")) {
-    return true;
-  }
-  bool match;
-  nsresult rv = NS_URIChainHasFlags(
-      aURI, nsIProtocolHandler::URI_IS_LOCAL_RESOURCE, &match);
-  if (NS_SUCCEEDED(rv) && match) {
-    return false;
-  }
-  // all other protocols are subject To CSP.
-  return true;
-}
-
 /*
  * A helper function for appending a CSP header to an existing CSP
  * policy.
  *
  * @param aCsp           the CSP policy
  * @param aHeaderValue   the header
  * @param aReportOnly    is this a report-only header?
  */

--- a/dom/security/nsCSPUtils.h
+++ b/dom/security/nsCSPUtils.h
@@ -183,19 +183,16 @@ inline CSPKeyword CSP_UTF16KeywordToEnum
     if (lowerKey.Equals(gCSPUTF16Keywords[i])) {
       return static_cast<CSPKeyword>(i);
     }
   }
   NS_ASSERTION(false, "Can not convert unknown Keyword to Enum");
   return CSP_LAST_KEYWORD_VALUE;
 }
 
-// Helper function to identify protocols and content types not subject to CSP.
-bool CSP_SubjectToCSP(nsIURI* aURI, nsContentPolicyType aContentType);
-
 nsresult CSP_AppendCSPFromHeader(nsIContentSecurityPolicy* aCsp,
                                  const nsAString& aHeaderValue,
                                  bool aReportOnly);
 
 /* =============== Helpers ================== */
 
 class nsCSPHostSrc;
 

--- a/dom/security/test/csp/file_pdfjs_not_subject_to_csp.html
+++ b/dom/security/test/csp/file_pdfjs_not_subject_to_csp.html
@@ -1,11 +1,11 @@
 <html>
 <head>
-  <meta http-equiv="Content-Security-Policy" content="script-src 'self' 'nonce-allowPDF'; base-uri 'self'">
+  <meta http-equiv="Content-Security-Policy" content="script-src 'self' 'nonce-allowPDF'">
 </head>
 <body>
 <iframe id="pdfFrame"></iframe>
 <br/>
 <button id="pdfButton">click to load pdf</button>
 <script nonce="allowPDF">
   async function loadPDFIntoIframe() {
     let response = await fetch("dummy.pdf");