Implement support for Math.imul in Crankshaft.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index a45caf4d4286f04ff7c1084d90d95ce2fa9181f1..5f6fce46524d04c0593ac9535f5e5370b70b780a 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -6271,6 +6271,16 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_NumberMod) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_NumberImul) {
+  NoHandleAllocation ha(isolate);
+  ASSERT(args.length() == 2);
+
+  CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]);
+  CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]);
+  return isolate->heap()->NumberFromInt32(x * y);
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_StringAdd) {
   NoHandleAllocation ha(isolate);
   ASSERT(args.length() == 2);