ImeSetComposition
Begins a new composition or updates the existing composition.
Blink has a special node (a composition node) that allows the input method to change text without affecting other DOM nodes.
This method may be called multiple times as the composition changes. When the client is done making changes the composition should either be canceled or completed. To cancel the composition call ImeCancelComposition. To complete the composition call either ImeCommitText or ImeFinishComposingText. Completion is usually signaled when: 1. The client receives a WM_IME_COMPOSITION message with a GCS_RESULTSTR flag (on Windows); 2. The client receives a "commit" signal of GtkIMContext (on Linux); 3. insertText of NSTextInput is called (on Mac).
This method is only used when window rendering is disabled.
Parameters
an optional set of ranges that will be underlined in the resulting text
an optional set of ranges that will be underlined in the resulting text
an optional range of the existing text that will be replaced(the value is only used on OS X)
an optional range of the resulting text that will be selected after insertion or replacement