story
Besides, Chrome didn't just introduce V8, it also introduced a cleaner UI, sandboxed tabs, and eventually, a much better set of DevTools than any other browser.
To deny that competition from Chrome didn't put pressure on other vendors I think is trying to willfully discount it's contributions for political, not technical reasons.
Chrome obviously put pressure on other vendors in various areas, including performance. What just isn't true is that without Chrome there would have been no JS performance competition. Whether the competition would have been as intense as it ended up being is a debatable counterfactual; I believe it would have been.
One other historical note, since you brought it up: Chrome was first announced publicly Sept 3, 2008. The first public beta of IE 8, with tabs in separate processes, was released on March 5, 2008. These processes ran in a low-privilege sandbox, as in fact did the entire browser starting with IE 7 (released October 2006), on Windows Vista or newer. Chrome did provide the first browser sandbox on Windows XP and non-Windows platforms, which was a big step up, of course. Again, there is a difference here between "introduced a new ground-breaking concept" and "incrementally improved on what was already going on".
Oh, and V8 was clearly considered a "threat" by other browser makers way before Chrome had any market share to speak of, so I'm not sure what your remark about Safari is supposed to mean.
The problem with this discussion is inherent in any counterfactual history, as you point out, and the common issue of what appears to be revolutionary to people outside a domain vs merely implementing things people have discussed for years, as the same "revolution" appears to people inside that domain.
The reality is that circa-2008 JS engines were fairly rudimentary, including (or especially) V8, and your average JIT compiler writer at the time would have been less impressed and more compelled to question why this "revolution" hadn't happened years earlier (and several did ask exactly that).
All that said, "Chrome put pressure on other vendors" has been extremely important to the evolution of JS performance, especially with Crankshaft -- I think it's extremely likely that shipping Firefox would still have a tracing JIT today and would be just starting to move past it without Crankshaft having existed -- but Chrome in that slot vs the other major browsers is really not that meaningful a distinction either, as without SpiderMonkey existing, it's likely that V8's major strides forward would have stopped with Crankshaft in 2010. Performance would have continued to improve in either (especially with JSC making big improvements), but I don't think we'd have seen the major architectural changes as often as we have without that pressure. Competition is great.
