Refactor ContentBrowserClient API exempting content scripts from CORB.

//services/network won't be able to directly use ContentBrowserClient,
so this CL refactors CORB-related parts of ContentBrowserClient in such
a way that the data they return in a browser-process can be easily
passed to the network service process.

Specifically, this CL changes the following ContentBrowserClient API:

  virtual bool ShouldBypassDocumentBlocking(const url::Origin& initiator,
                                            const GURL& url,
                                            ResourceType resource_type);

into:

  virtual const char* GetInitatorSchemeBypassingDocumentBlocking();

Bug: 792546
Change-Id: I39d88a97ff24d776319b2687837838fa594054c5
Tbr: rdevlin.cronin@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/958041
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Reviewed-by: Nick Carter <nick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542897}

chrome/browser/chrome_content_browser_client.cc

@@ -1301,18 +1301,19 @@ bool ChromeContentBrowserClient::ShouldLockToOrigin(
   return true;
 }
 
-bool ChromeContentBrowserClient::ShouldBypassDocumentBlocking(
-    const url::Origin& initiator,
-    const GURL& url,
-    ResourceType resource_type) {
+const char*
+ChromeContentBrowserClient::GetInitatorSchemeBypassingDocumentBlocking() {
 #if BUILDFLAG(ENABLE_EXTENSIONS)
-  if (ChromeContentBrowserClientExtensionsPart::ShouldBypassDocumentBlocking(
-          initiator)) {
-    return true;
-  }
+  // Don't block responses for extension processes or for content scripts.
+  // TODO(creis): When every extension fetch (including content scripts) has
+  // been made to go through an extension-specific URLLoaderFactory, this
+  // mechanism ought to work by enumerating the host permissions from the
+  // extension manifest, and forwarding them on to the network service while
+  // brokering the URLLoaderFactory.
+  return extensions::kExtensionScheme;
+#else
+  return nullptr;
 #endif
-
-  return false;
 }
 
 // These are treated as WebUI schemes but do not get WebUI bindings. Also,

chrome/browser/chrome_content_browser_client.h

@@ -111,10 +111,7 @@ class ChromeContentBrowserClient : public content::ContentBrowserClient {
                                        const GURL& effective_site_url) override;
   bool ShouldLockToOrigin(content::BrowserContext* browser_context,
                           const GURL& effective_site_url) override;
-  bool ShouldBypassDocumentBlocking(
-      const url::Origin& initiator,
-      const GURL& url,
-      content::ResourceType resource_type) override;
+  const char* GetInitatorSchemeBypassingDocumentBlocking() override;
   void GetAdditionalWebUISchemes(
       std::vector<std::string>* additional_schemes) override;
   void GetAdditionalViewSourceSchemes(

chrome/browser/extensions/chrome_content_browser_client_extensions_part.cc

@@ -394,14 +394,6 @@ bool ChromeContentBrowserClientExtensionsPart::ShouldLockToOrigin(
   return true;
 }
 
-bool ChromeContentBrowserClientExtensionsPart::ShouldBypassDocumentBlocking(
-    const url::Origin& initiator) {
-  // Don't block responses for extension processes or for content scripts.
-  // TODO(creis): This check can be made stricter by checking what the extension
-  // has access to.
-  return initiator.scheme() == extensions::kExtensionScheme;
-}
-
 // static
 bool ChromeContentBrowserClientExtensionsPart::CanCommitURL(
     content::RenderProcessHost* process_host, const GURL& url) {

chrome/browser/extensions/chrome_content_browser_client_extensions_part.h

@@ -40,7 +40,6 @@ class ChromeContentBrowserClientExtensionsPart
       const GURL& effective_site_url);
   static bool ShouldLockToOrigin(content::BrowserContext* browser_context,
                                  const GURL& effective_site_url);
-  static bool ShouldBypassDocumentBlocking(const url::Origin& initiator);
   static bool CanCommitURL(content::RenderProcessHost* process_host,
                            const GURL& url);
   static bool IsSuitableHost(Profile* profile,

content/browser/loader/cross_site_document_resource_handler.cc

@@ -778,17 +778,21 @@ bool CrossSiteDocumentResourceHandler::ShouldBlockBasedOnHeaders(
   if (initiator.scheme() == url::kFileScheme)
     return false;
 
+  // Give embedder a chance to skip document blocking for this response.
+  const char* initiator_scheme_exception =
+      GetContentClient()
+          ->browser()
+          ->GetInitatorSchemeBypassingDocumentBlocking();
+  if (initiator_scheme_exception &&
+      initiator.scheme() == initiator_scheme_exception) {
+    return false;
+  }
+
   // Only block if this is a request made from a renderer process.
   const ResourceRequestInfoImpl* info = GetRequestInfo();
   if (!info || info->GetChildID() == -1)
     return false;
 
-  // Give embedder a chance to skip document blocking for this response.
-  if (GetContentClient()->browser()->ShouldBypassDocumentBlocking(
-          initiator, url, info->GetResourceType())) {
-    return false;
-  }
-
   // Allow the response through if it has valid CORS headers.
   std::string cors_header;
   response->head.headers->GetNormalizedHeader("access-control-allow-origin",

content/public/browser/content_browser_client.cc

@@ -93,11 +93,8 @@ bool ContentBrowserClient::ShouldLockToOrigin(BrowserContext* browser_context,
   return true;
 }
 
-bool ContentBrowserClient::ShouldBypassDocumentBlocking(
-    const url::Origin& initiator,
-    const GURL& url,
-    ResourceType resource_type) {
-  return false;
+const char* ContentBrowserClient::GetInitatorSchemeBypassingDocumentBlocking() {
+  return nullptr;
 }
 
 void ContentBrowserClient::GetAdditionalViewSourceSchemes(

content/public/browser/content_browser_client.h

@@ -257,12 +257,10 @@ class CONTENT_EXPORT ContentBrowserClient {
   virtual bool ShouldLockToOrigin(BrowserContext* browser_context,
                                   const GURL& effective_url);
 
-  // Returns true if the |initiator| origin should be allowed to receive a
-  // document at |url|, bypassing the usual blocking logic. Defaults to false.
-  // This is called on the IO thread.
-  virtual bool ShouldBypassDocumentBlocking(const url::Origin& initiator,
-                                            const GURL& url,
-                                            ResourceType resource_type);
+  // Returns the scheme of request initiator that should be ignored by
+  // cross-origin read blocking.  nullptr can be returned to indicate that no
+  // exceptions should be granted based on initiator's scheme.
+  virtual const char* GetInitatorSchemeBypassingDocumentBlocking();
 
   // Returns a list additional WebUI schemes, if any.  These additional schemes
   // act as aliases to the chrome: scheme.  The additional schemes may or may