Improve IDB module's SecurityError messages.

Source/modules/navigatorcontentutils/NavigatorContentUtils.cpp

Index: Source/modules/navigatorcontentutils/NavigatorContentUtils.cpp
diff --git a/Source/modules/navigatorcontentutils/NavigatorContentUtils.cpp b/Source/modules/navigatorcontentutils/NavigatorContentUtils.cpp
index df33faf653a043e35e7e35c781a7440d448ab64e..cf2a34e80b49f23f8d1038e71ed9a21553879863 100644
--- a/Source/modules/navigatorcontentutils/NavigatorContentUtils.cpp
+++ b/Source/modules/navigatorcontentutils/NavigatorContentUtils.cpp
@@ -29,6 +29,7 @@
 
 #if ENABLE(NAVIGATOR_CONTENT_UTILS)
 
+#include "bindings/v8/ExceptionMessages.h"
 #include "bindings/v8/ExceptionState.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
@@ -109,13 +110,16 @@ static bool verifyProtocolHandlerScheme(const String& scheme, ExceptionState& es
         // The specification requires that the length of scheme is at least five characteres (including 'web+' prefix).
         if (scheme.length() >= 5 && isValidProtocol(scheme))
             return true;
-        es.throwDOMException(SecurityError);
+        if (scheme.length() < 5)
+            es.throwSecurityError(ExceptionMessages::failedToExecute("registerProtocolHandler", "Navigator", "the scheme length (including 'web+') must be at least 5 characters."));
+        else
+            es.throwSecurityError(ExceptionMessages::failedToExecute("registerProtocolHandler", "Navigator", "the scheme '" + scheme + "' may not be registered."));
         return false;
     }
 
     if (isProtocolWhitelisted(scheme))
         return true;
-    es.throwDOMException(SecurityError);
+    es.throwSecurityError(ExceptionMessages::failedToExecute("registerProtocolHandler", "Navigator", "the scheme '" + scheme + "' may not be registered."));
     return false;
 }