Improve error message in navigator.requestMediaKeySystemAccess()

Source/modules/encryptedmedia/NavigatorRequestMediaKeySystemAccess.cpp

Index: Source/modules/encryptedmedia/NavigatorRequestMediaKeySystemAccess.cpp
diff --git a/Source/modules/encryptedmedia/NavigatorRequestMediaKeySystemAccess.cpp b/Source/modules/encryptedmedia/NavigatorRequestMediaKeySystemAccess.cpp
index a9768db0864e179d61317c1ad854355b6e6cf07e..02879839b9f6f04f1cc7b8323139c10b0119df05 100644
--- a/Source/modules/encryptedmedia/NavigatorRequestMediaKeySystemAccess.cpp
+++ b/Source/modules/encryptedmedia/NavigatorRequestMediaKeySystemAccess.cpp
@@ -193,7 +193,7 @@ ScriptPromise NavigatorRequestMediaKeySystemAccess::requestMediaKeySystemAccess(
     Document* document = toDocument(executionContext);
     if (!document->page()) {
         return ScriptPromise::rejectWithDOMException(
-            scriptState, DOMException::create(InvalidStateError, "Document does not have a page."));
+            scriptState, DOMException::create(InvalidStateError, "The context provided is not associated with a page."));
     }
 
     MediaKeySystemAccessInitializer* initializer = new MediaKeySystemAccessInitializer(scriptState, keySystem, supportedConfigurations);