remove Isolate::Current from most files starting with 'f' through 'i'

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 8eace1268481c1011607548a610c37f1a31625f6..e54765d0346261b6be3241d74651522318482842 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1385,15 +1385,8 @@ class SaveContext BASE_EMBEDDED {
   inline explicit SaveContext(Isolate* isolate);
 
   ~SaveContext() {
-    if (context_.is_null()) {
-      Isolate* isolate = Isolate::Current();
-      isolate->set_context(NULL);
-      isolate->set_save_context(prev_);
-    } else {
-      Isolate* isolate = context_->GetIsolate();
-      isolate->set_context(*context_);
-      isolate->set_save_context(prev_);
-    }
+    isolate_->set_context(context_.is_null() ? NULL : *context_);
+    isolate_->set_save_context(prev_);
   }
 
   Handle<Context> context() { return context_; }
@@ -1405,6 +1398,7 @@ class SaveContext BASE_EMBEDDED {
   }
 
  private:
+  Isolate* isolate_;
   Handle<Context> context_;
   SaveContext* prev_;
   Address c_entry_fp_;