Have HTMLMediaElement::play() return a Promise.

third_party/WebKit/Source/core/dom/DOMException.cpp

Index: third_party/WebKit/Source/core/dom/DOMException.cpp
diff --git a/third_party/WebKit/Source/core/dom/DOMException.cpp b/third_party/WebKit/Source/core/dom/DOMException.cpp
index a8b1414ebac5629ed43768d09c9953887f6c5821..3dc08290745fdf80dd20106d4aa23f7e32972b06 100644
--- a/third_party/WebKit/Source/core/dom/DOMException.cpp
+++ b/third_party/WebKit/Source/core/dom/DOMException.cpp
@@ -37,6 +37,7 @@ static const struct CoreException {
     const char* const message;
     const int code;
 } coreExceptions[] = {
+    // This list must be kept in sync with the one in ExceptionCode.h
     { "IndexSizeError", "Index or size was negative, or greater than the allowed value.", 1 },
     { "HierarchyRequestError", "A Node was inserted somewhere it doesn't belong.", 3 },
     { "WrongDocumentError", "A Node was used in a different document than the one that created it (that doesn't support it).", 4 },
@@ -81,6 +82,12 @@ static const struct CoreException {
 
     // Push API
     { "PermissionDeniedError", "User or security policy denied the request.", 0 },
+
+    // Used by HTML and Media Session API.
+    { "NotAllowedError", "The request is not allowed by the user agent or the platform in the current context.", 0 },
+
+    // Please add new entries at the end of this list to guarantee any ordering
+    // expectations.
 };
 
 static const CoreException* getErrorEntry(ExceptionCode ec)