[Interpreter] Add support for for count operations.

src/interpreter/bytecode-array-builder.cc

Index: src/interpreter/bytecode-array-builder.cc
diff --git a/src/interpreter/bytecode-array-builder.cc b/src/interpreter/bytecode-array-builder.cc
index a41d332a307db4f2e6e57d1bde2f6fcb3873f996..7fb5e949a11b815d860618265f8fed5a43124264 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -172,6 +172,17 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::BinaryOperation(Token::Value op,
 }
 
 
+BytecodeArrayBuilder& BytecodeArrayBuilder::CountOperation(Token::Value op,
+                                                           Strength strength) {
+  if (is_strong(strength)) {
+    UNIMPLEMENTED();
+  }
+
+  Output(BytecodeForCountOperation(op));
+  return *this;
+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::LogicalNot() {
   Output(Bytecode::kLogicalNot);
   return *this;
@@ -465,6 +476,14 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::CastAccumulatorToName() {
 }
 
 
+BytecodeArrayBuilder& BytecodeArrayBuilder::CastAccumulatorToNumber() {
+  // TODO(rmcilroy): consider omitting if the preceeding bytecode always returns
+  // a number.
+  Output(Bytecode::kToNumber);
+  return *this;
+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::Bind(BytecodeLabel* label) {
   if (label->is_forward_target()) {
     // An earlier jump instruction refers to this label. Update it's location.
@@ -827,6 +846,20 @@ Bytecode BytecodeArrayBuilder::BytecodeForBinaryOperation(Token::Value op) {
 
 
 // static
+Bytecode BytecodeArrayBuilder::BytecodeForCountOperation(Token::Value op) {
+  switch (op) {
+    case Token::Value::ADD:
+      return Bytecode::kInc;
+    case Token::Value::SUB:
+      return Bytecode::kDec;
+    default:
+      UNREACHABLE();
+      return static_cast<Bytecode>(-1);
+  }
+}
+
+
+// static
 Bytecode BytecodeArrayBuilder::BytecodeForCompareOperation(Token::Value op) {
   switch (op) {
     case Token::Value::EQ: