Add DCHECKs to validate ProfileIOData's list of protocols.

chrome/browser/custom_handlers/protocol_handler_registry.cc

Index: chrome/browser/custom_handlers/protocol_handler_registry.cc
diff --git a/chrome/browser/custom_handlers/protocol_handler_registry.cc b/chrome/browser/custom_handlers/protocol_handler_registry.cc
index 596682630c3681d2be89ec853dc14be19117e1ab..82f75e256e1104607f8f385fd66bca20cecc08c6 100644
--- a/chrome/browser/custom_handlers/protocol_handler_registry.cc
+++ b/chrome/browser/custom_handlers/protocol_handler_registry.cc
@@ -238,6 +238,7 @@ void ProtocolHandlerRegistry::Delegate::RegisterExternalHandler(
     const std::string& protocol) {
   ChildProcessSecurityPolicy* policy =
     ChildProcessSecurityPolicy::GetInstance();
+  CHECK(CanSchemeBeOverridden(protocol));
   if (!policy->IsWebSafeScheme(protocol)) {
     policy->RegisterWebSafeScheme(protocol);
   }
@@ -247,11 +248,11 @@ void ProtocolHandlerRegistry::Delegate::DeregisterExternalHandler(
     const std::string& protocol) {
 }
 
-bool ProtocolHandlerRegistry::Delegate::IsExternalHandlerRegistered(
+bool ProtocolHandlerRegistry::Delegate::CanSchemeBeOverridden(
     const std::string& protocol) {
   // NOTE(koz): This function is safe to call from any thread, despite living
   // in ProfileIOData.
-  return ProfileIOData::IsHandledProtocol(protocol);
+  return !ProfileIOData::IsBuiltInProtocol(protocol);
 }
 
 scoped_refptr<shell_integration::DefaultProtocolClientWorker>
@@ -480,12 +481,10 @@ void ProtocolHandlerRegistry::GetRegisteredProtocols(
 bool ProtocolHandlerRegistry::CanSchemeBeOverridden(
     const std::string& scheme) const {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  const ProtocolHandlerList* handlers = GetHandlerList(scheme);
-  // If we already have a handler for this scheme, we can add more.
-  if (handlers != NULL && !handlers->empty())
-    return true;
-  // Don't override a scheme if it already has an external handler.
-  return !delegate_->IsExternalHandlerRegistered(scheme);
+
+  // Don't override a scheme if it has an built-in handler (http, https, chrome-
+  // extension, etc).
+  return delegate_->CanSchemeBeOverridden(scheme);
 }
 
 bool ProtocolHandlerRegistry::IsRegistered(
@@ -795,7 +794,11 @@ void ProtocolHandlerRegistry::RegisterProtocolHandler(
     const ProtocolHandler& handler,
     const HandlerSource source) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  DCHECK(CanSchemeBeOverridden(handler.protocol()));
+  if (!CanSchemeBeOverridden(handler.protocol())) {
+    NOTREACHED();
+    return;
+  }
+
   DCHECK(!handler.IsEmpty());
   ProtocolHandlerMultiMap& map =
       (source == POLICY) ? policy_protocol_handlers_ : user_protocol_handlers_;
@@ -805,7 +808,7 @@ void ProtocolHandlerRegistry::RegisterProtocolHandler(
   if (IsRegistered(handler)) {
     return;
   }
-  if (enabled_ && !delegate_->IsExternalHandlerRegistered(handler.protocol()))
+  if (enabled_)
     delegate_->RegisterExternalHandler(handler.protocol());
   InsertHandler(handler);
 }