Lazily initialize fast_sqrt() and pass an Isolate parameter to it

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index 5baf1a8e1bf4894d06991da097dd8f8e9035c3d0..82052301d4b079c7785182983c66e59dc1a62e29 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -64,14 +64,14 @@ UnaryMathFunctionWithIsolate CreateExpFunction(Isolate* isolate) {
 }
 
 
-UnaryMathFunction CreateSqrtFunction() {
+UnaryMathFunctionWithIsolate CreateSqrtFunction(Isolate* isolate) {
   size_t actual_size;
   // Allocate buffer in executable space.
   byte* buffer =
       static_cast<byte*>(base::OS::Allocate(1 * KB, &actual_size, true));
-  if (buffer == NULL) return &std::sqrt;
+  if (buffer == nullptr) return nullptr;
 
-  MacroAssembler masm(NULL, buffer, static_cast<int>(actual_size),
+  MacroAssembler masm(isolate, buffer, static_cast<int>(actual_size),
                       CodeObjectRequired::kNo);
   // xmm0: raw double input.
   // Move double input into registers.
@@ -82,9 +82,9 @@ UnaryMathFunction CreateSqrtFunction() {
   masm.GetCode(&desc);
   DCHECK(!RelocInfo::RequiresRelocation(desc));
 
-  Assembler::FlushICacheWithoutIsolate(buffer, actual_size);
+  Assembler::FlushICache(isolate, buffer, actual_size);
   base::OS::ProtectCode(buffer, actual_size);
-  return FUNCTION_CAST<UnaryMathFunction>(buffer);
+  return FUNCTION_CAST<UnaryMathFunctionWithIsolate>(buffer);
 }