Add Forest API for logical expressions

Change-Id: Ib9efeb06d1c6857b07f3c42724310621416a0fc8
Reviewed-on: https://dart-review.googlesource.com/57080
Reviewed-by: Dan Rubel <danrubel@google.com>
Reviewed-by: Peter von der Ahé <ahe@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/lib/src/fasta/ast_building_factory.dart

@@ -413,6 +413,11 @@ class AstBuildingForest
     throw new UnimplementedError();
   }
 
+  @override
+  Expression logicalExpression(
+          Expression leftOperand, Token operator, Expression rightOperand) =>
+      astFactory.binaryExpression(leftOperand, operator, rightOperand);
+
   @override
   Object mapEntry(Expression key, Token colon, Expression value) =>
       astFactory.mapLiteralEntry(key, colon, value);

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

@@ -1037,13 +1037,10 @@ abstract class BodyBuilder<Expression, Statement, Arguments>
   void doLogicalExpression(Token token) {
     Expression argument = popForValue();
     Expression receiver = pop();
-    var logicalExpression = new ShadowLogicalExpression(
-        toKernelExpression(receiver),
-        token.stringValue,
-        toKernelExpression(argument))
-      ..fileOffset = offsetForToken(token);
+    Expression logicalExpression =
+        forest.logicalExpression(receiver, token, argument);
     typePromoter.exitLogicalExpression(
-        toKernelExpression(argument), logicalExpression);
+        toKernelExpression(argument), toKernelExpression(logicalExpression));
     push(logicalExpression);
   }
 

pkg/front_end/lib/src/fasta/kernel/fangorn.dart

@@ -83,6 +83,7 @@ import 'kernel_shadow_ast.dart'
         ShadowLabeledStatement,
         ShadowListLiteral,
         ShadowLoadLibrary,
+        ShadowLogicalExpression,
         ShadowMapLiteral,
         ShadowNot,
         ShadowNullLiteral,
@@ -426,6 +427,14 @@ class Fangorn extends Forest<Expression, Statement, Token, Arguments> {
           LabelTarget<Statement> target, Statement statement) =>
       statement;
 
+  @override
+  Expression logicalExpression(
+      Expression leftOperand, Token operator, Expression rightOperand) {
+    return new ShadowLogicalExpression(
+        leftOperand, operator.stringValue, rightOperand)
+      ..fileOffset = offsetForToken(operator);
+  }
+
   @override
   Expression notExpression(Expression operand, Token token) {
     return new ShadowNot(operand)..fileOffset = offsetForToken(token);

pkg/front_end/lib/src/fasta/kernel/forest.dart

@@ -250,6 +250,11 @@ abstract class Forest<Expression, Statement, Location, Arguments> {
   Statement labeledStatement(
       LabelTarget<Statement> target, Statement statement);
 
+  /// Return a representation of a logical expression having the [leftOperand],
+  /// [rightOperand] and the [operator] (either `&&` or `||`).
+  Expression logicalExpression(
+      Expression leftOperand, Location operator, Expression rightOperand);
+
   Expression notExpression(Expression operand, Location location);
 
   /// Return a representation of a parenthesized condition consisting of the