GN: Build rules and fixes for (almost) all mojo unittest targets

mojo/common/BUILD.gn

Index: mojo/common/BUILD.gn
diff --git a/mojo/common/BUILD.gn b/mojo/common/BUILD.gn
index 72171ba3a972d2a123ba51a347cc0826e56533bb..5bd139f8c7245ad68ff118e6d3dd0c055f2d1a06 100644
--- a/mojo/common/BUILD.gn
+++ b/mojo/common/BUILD.gn
@@ -27,5 +27,29 @@ component("common") {
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
+    "//url",
   ] + mojo_system_for_component
 }
+
+# GYP version: mojo/mojo_base.gyp:mojo_common_unittests
+test("mojo_common_unittests") {
+  deps = [
+    ":common",
+    "//base",
+    "//base:message_loop_tests",
+    "//mojo/common/test:run_all_unittests",
+    "//mojo/common/test:test_support",
+    "//mojo/environment:chromium",
+    "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/test_support:test_utils",
+    "//testing/gtest",
+    "//url",
+  ]
+
+  sources = [
+    "common_type_converters_unittest.cc",
+    "handle_watcher_unittest.cc",
+    "message_pump_mojo_unittest.cc",
+    "test/multiprocess_test_helper_unittest.cc",
+  ]
+}