Actually, we use twice nsTextEditorState::GetValue call per HTMLInputElement::SetValue call. nsTextEditorState::GetValue spends 10% of HTMLInputElement::SetValue, so we should remove twice call.

Comment on attachment 8877538 [details] Bug 1368888 - Don't get previous value twice in input.value setter. https://reviewboard.mozilla.org/r/149000/#review153448 ::: commit-message-b266a:3 (Diff revision 1) > +Bug 1368888 - Don't get previous value twice in input.value setter. r?smaug > + > +Actually, we get previous input.value twice in HTMLInputElement::SetValue and nsTextEditorState::SetValue when setting input.value. Since nsTextEditorState::GetValue uses DocumentEncoder, it is expensive. So we should use old value as parameter of nsTextEditorState::SetValue if possible. Drop "Actually," ::: dom/html/HTMLInputElement.h:946 (Diff revision 1) > * > * @param aValue String to set. > * @param aFlags See nsTextEditorState::SetValueFlags. > */ > - nsresult SetValueInternal(const nsAString& aValue, uint32_t aFlags); > + nsresult SetValueInternal(const nsAString& aValue, > + const nsAString* aOldValue, This needs some comment. I thought first this was out-param, but apparently aOldValue is in-param ::: dom/html/nsTextEditorState.cpp:2530 (Diff revision 1) > } else { > // If setting value won't change current value, we shouldn't commit > // composition for compatibility with the other browsers. > nsAutoString currentValue; > + if (aOldValue) { > + currentValue.Assign(*aOldValue); Please add some #ifdef DEBUG code here to ensure aOldValue equals the value one would get from mBoundFrame->GetText() ::: dom/html/nsTextEditorState.cpp:2605 (Diff revision 1) > } > #endif > > nsAutoString currentValue; > + if (aOldValue) { > + currentValue.Assign(*aOldValue); Also here. Add #ifdef DEBUG code to ensure aOldValue equals with value from mBoundFrame->GetText

Comment on attachment 8877538 [details] Bug 1368888 - Don't get previous value twice in input.value setter. Could you additional review? During committing composition, nsTextEditorState::GetValue and mBoundFrame->GetText might not return same value. So we don't trust old value during it.

Comment on attachment 8877538 [details] Bug 1368888 - Don't get previous value twice in input.value setter. https://reviewboard.mozilla.org/r/149000/#review154410

Pushed by m_kato@ga2.so-net.ne.jp: https://hg.mozilla.org/integration/autoland/rev/4b9cc1cd08ea Don't get previous value twice in input.value setter. r=smaug