Bug 944681 - Don't fire inputcontextchange on selection change from mouseup. r=yxl

--HG--
extra : rebase_source : bd6286e8bdec2ceb081d837d9341b54ca69a1886

dom/inputmethod/forms.js

@@ -396,7 +396,6 @@ let FormAssistant = {
         range = getSelectionRange(this.focusedElement);
         if (range[0] !== this.selectionStart ||
             range[1] !== this.selectionEnd) {
-          this.sendKeyboardState(this.focusedElement);
           this.updateSelection();
         }
         break;