Clean up and simplify Parser::Declare

This removes the "resolve" parameter from Declare, since there's no case
where Scope analysis wouldn't make the same resolution decision the
parser can make here.

Other cleanup includes:
  - Replace some if statements with DCHECKS where they could never be hit
  - After the above, reordered some conditions for clarity
  - Remove or edit down old comments

Should be no change in behavior.

R=neis@chromium.org

Review-Url: https://codereview.chromium.org/2217973003
Cr-Commit-Position: refs/heads/master@{#38454}

src/parsing/parser.h

@@ -1082,8 +1082,8 @@ class Parser : public ParserBase<ParserTraits> {
   // Parser support
   VariableProxy* NewUnresolved(const AstRawString* name, VariableMode mode);
   Variable* Declare(Declaration* declaration,
-                    DeclarationDescriptor::Kind declaration_kind, bool resolve,
-                    bool* ok, Scope* declaration_scope = nullptr);
+                    DeclarationDescriptor::Kind declaration_kind, bool* ok,
+                    Scope* declaration_scope = nullptr);
   void DeclareConstVariable(const AstRawString* name, InitializationFlag init,
                             int pos, bool* ok);
 

src/parsing/pattern-rewriter.cc

@@ -151,9 +151,8 @@ void Parser::PatternRewriter::VisitVariableProxy(VariableProxy* pattern) {
   Declaration* declaration = factory()->NewVariableDeclaration(
       proxy, descriptor_->mode, descriptor_->scope,
       descriptor_->declaration_pos);
-  Variable* var =
-      parser_->Declare(declaration, descriptor_->declaration_kind,
-                       descriptor_->mode != VAR, ok_, descriptor_->hoist_scope);
+  Variable* var = parser_->Declare(declaration, descriptor_->declaration_kind,
+                                   ok_, descriptor_->hoist_scope);
   if (!*ok_) return;
   DCHECK_NOT_NULL(var);
   DCHECK(!proxy->is_resolved() || proxy->var() == var);