Revert of Remove a Platform::current() check from Mojo's error handler in WebSocket

third_party/WebKit/Source/modules/websockets/WebSocketHandleImpl.cpp

Index: third_party/WebKit/Source/modules/websockets/WebSocketHandleImpl.cpp
diff --git a/third_party/WebKit/Source/modules/websockets/WebSocketHandleImpl.cpp b/third_party/WebKit/Source/modules/websockets/WebSocketHandleImpl.cpp
index 3748b0f9644de331e5196dbd0a29463dffd74718..304b9e7f50b5479d98d559115708b264ecf3d726 100644
--- a/third_party/WebKit/Source/modules/websockets/WebSocketHandleImpl.cpp
+++ b/third_party/WebKit/Source/modules/websockets/WebSocketHandleImpl.cpp
@@ -124,6 +124,15 @@ void WebSocketHandleImpl::disconnect()
 
 void WebSocketHandleImpl::onConnectionError()
 {
+    if (!blink::Platform::current()) {
+        // In the renderrer shutdown sequence, mojo channels are destructed and this
+        // function is called. On the other hand, blink objects became invalid
+        // *silently*, which means we must not touch |*client_| any more.
+        // TODO(yhirano): Remove this code once the shutdown sequence is fixed.
+        disconnect();
+        return;
+    }
+
     // Our connection to the WebSocket was dropped. This could be due to
     // exceeding the maximum number of concurrent websockets from this process.