dart2js: add function coverage tracking in dart2js output, dumpinfo, and

sdk/lib/_internal/js_runtime/lib/js_helper.dart

Index: sdk/lib/_internal/js_runtime/lib/js_helper.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/js_helper.dart b/sdk/lib/_internal/js_runtime/lib/js_helper.dart
index 7cd2c69d7300d5143bbe7e3412e1698208c5b41e..7f099b8ccf18d01041c85d3aef5c7f4fe4f618a8 100644
--- a/sdk/lib/_internal/js_runtime/lib/js_helper.dart
+++ b/sdk/lib/_internal/js_runtime/lib/js_helper.dart
@@ -20,7 +20,8 @@ import 'dart:_js_embedded_names' show
     JsGetName,
     LEAF_TAGS,
     NATIVE_SUPERCLASS_TAG_NAME,
-    STATIC_FUNCTION_NAME_PROPERTY_NAME;
+    STATIC_FUNCTION_NAME_PROPERTY_NAME,
+    TRACE_BUFFER;
 
 import 'dart:collection';
 
@@ -260,7 +261,7 @@ void throwInvalidReflectionError(String memberName) {
 /// Helper to print the given method information to the console the first
 /// time it is called with it.
 @NoInline()
-void traceHelper(String method) {
+void consoleTraceHelper(String method) {
   if (JS('bool', '!this.cache')) {
     JS('', 'this.cache = Object.create(null)');
   }
@@ -270,6 +271,31 @@ void traceHelper(String method) {
   }
 }
 
+List _traceBuffer;
+
+/// Helper to send coverage information as a POST request to a server.
+@NoInline()
+void postTraceHelper(int id, String name) {
+  // Note: we can't move this initialization to the declaration of
+  // [_traceBuffer] because [postTraceHelper] is called very early on functions
+  // that define constants, this happens before getters and setters are expanded
+  // and before main starts executing. This initialization here allows us to
+  // skip the lazy field initialization logic.
+  if (_traceBuffer == null) _traceBuffer = JS('JSArray', '[]');
+  if (JS('bool', '#.length == 0', _traceBuffer)) {
+    JS('', r'''
+      window.setTimeout((function(buffer) {
+        return function() {
+          var xhr = new XMLHttpRequest();
+          xhr.open("POST", "/coverage_uri_to_amend_by_server");
+          xhr.send(JSON.stringify(buffer));
+          buffer.length = 0;
+        };
+      })(#), 1000)''', _traceBuffer);
+  }
+  JS('', '#.push([#, #])', _traceBuffer, id, name);
+}
+
 class JSInvocationMirror implements Invocation {
   static const METHOD = 0;
   static const GETTER = 1;