Remove educated guesses/assumptions that are likely false.

Thanks @peggyl for helping research.

Minor other tweaks.

Author: dmitshur

_posts/blog/2015-09-28-surprises-in-gopherjs-performance.mdown

@@ -250,15 +250,14 @@ sys     0m0.004s
 ```
 
 Nice, it's the same time as the Go and GopherJS versions.
-So that means a few things.
+That means a few things.
 
-The V8 JavaScript Engine is incredible.
+The V8 JavaScript engine is incredible.
 It's able to take Go code that is compiled to JavaScript code, and just-in-time compile to it to machine instructions that are as efficient as the native Go compiler.
 
-The JavaScript `Math.pow` implementation clearly has a fast-path for when value of x is -1 and values of y are integers.
-So for those inputs, it's faster.
-Using `Pow` with such inputs is silly and should not be done, as you can see by the 50 million to 1 billion iteration increase when rewriting it with an equivalent if statement.
-Go chooses not to have a fast path for such inputs, which makes it faster in the general case, and I'm glad it makes that choice.
+The JavaScript `Math.pow` implementation is faster when value of x is -1 and values of y are integers.
+I haven't compared its performance for other inputs; let me know if you do.
+However, using `Pow` with such inputs is silly and should not be done, as you can see by the 50 million to 1 billion iteration increase when rewriting it with an equivalent if statement.
 
 You can try the final optimized version of GopherJS in your browser via the GopherJS Playground: