Revert "[parser] Remove pretenuring of closures assigned to properties"

This reverts commit 20e346bd.

Reason for revert: tanks bluebird-doxbee

Original change's description:
> [parser] Remove pretenuring of closures assigned to properties
> 
> This pretenuring was added in https://codereview.chromium.org/5220007,
> back when it was necessary in order to allow use of the closure
> as a "constant function" property. This should no longer be the case,
> and the pretenuring causes some unfortunate downstream effects.
> 
> This patch removes the parser's setting of this bit. If it doesn't
> cause regressions on the perf bots, followup CLs will remove the
> rest of the support for this feature.
> 
> Bug: v8:7442
> Change-Id: I27c43dd4293ce5de921be6c78571e712778d138a
> Reviewed-on: https://chromium-review.googlesource.com/914610
> Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
> Commit-Queue: Adam Klein <adamk@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#51254}

Change-Id: I3e133046a4df64792a6652227d419239c628dbfb
Tbr: gsathya@chromium.org
Bug: v8:7442
Reviewed-on: https://chromium-review.googlesource.com/917701Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51280}

src/parsing/parser-base.h

@@ -2982,6 +2982,8 @@ ParserBase<Impl>::ParseAssignmentExpression(bool accept_IN, bool* ok) {
     function_state_->AddProperty();
   }
 
+  impl()->CheckAssigningFunctionLiteralToProperty(expression, right);
+
   if (fni_ != nullptr) {
     // Check if the right hand side is a call to avoid inferring a
     // name if we're dealing with "a = function(){...}();"-like

src/parsing/parser.h

@@ -742,6 +742,16 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
     fni_->Infer();
   }
 
+  // If we assign a function literal to a property we pretenure the
+  // literal so it can be added as a constant function property.
+  V8_INLINE static void CheckAssigningFunctionLiteralToProperty(
+      Expression* left, Expression* right) {
+    DCHECK_NOT_NULL(left);
+    if (left->IsProperty() && right->IsFunctionLiteral()) {
+      right->AsFunctionLiteral()->set_pretenure();
+    }
+  }
+
   // Determine if the expression is a variable proxy and mark it as being used
   // in an assignment or with a increment/decrement operator.
   V8_INLINE static void MarkExpressionAsAssigned(Expression* expression) {

src/parsing/preparser.h

@@ -1298,6 +1298,9 @@ class PreParser : public ParserBase<PreParser> {
       const PreParserExpression& expression) {}
   V8_INLINE static void InferFunctionName() {}
 
+  V8_INLINE static void CheckAssigningFunctionLiteralToProperty(
+      const PreParserExpression& left, const PreParserExpression& right) {}
+
   V8_INLINE void MarkExpressionAsAssigned(
       const PreParserExpression& expression) {
     // TODO(marja): To be able to produce the same errors, the preparser needs