Introduce dartanalyze into our build.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index d23d33e122fd88014173ae83a2278abed504f723..748d546db5963f1c185add654fea38797df96fd3 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -24,6 +24,21 @@ group("default") {
   }
 }
 
+# A group which invokes the dart checker on each dart package. This can take
+# multiple seconds per target.
+group("check") {
+  testonly = true
+  deps = [
+    "//examples/dart/console_example:console_example_analyze",
+    "//examples/dart/hello_world/hello:hello_analyze",
+    "//examples/dart/hello_world/world:world_analyze",
+    "//examples/dart/wget:wget_analyze",
+    "//services/dart/test/echo:echo_analyze",
+    "//services/dart/test/pingpong:pingpong_analyze",
+    "//services/dart/test/pingpong_target:pingpong_target_analyze",
+  ]
+}
+
 # Deprecated name for the default build target.
 group("root") {
   testonly = true