X87: Make fast_exp take an Isolate* paramter.

  port 0fb2edd1 (r32217)

  original commit message:
  We still share the code globally, but if we wanted, it would be easy to
  make it per isolate now

BUG=

Review URL: https://codereview.chromium.org/1477683002

Cr-Commit-Position: refs/heads/master@{#32242}

src/x87/codegen-x87.cc

@@ -32,11 +32,10 @@ void StubRuntimeCallHelper::AfterCall(MacroAssembler* masm) const {
 
 
 #define __ masm.
+double x87_std_exp(double x, Isolate* isolate) { return std::exp(x); }
 
-
-UnaryMathFunction CreateExpFunction() {
-  // No SSE2 support
-  return nullptr;
+UnaryMathFunctionWithIsolate CreateExpFunction(Isolate* isolate) {
+  return x87_std_exp;
 }