Run the webkit layout tests under swarming on linux_chromium_rel_ng.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index cabb6818fa2bb59ed0c1c1a796648e388bc8609f..ef5c89457b4d306693b444d95c042732aa5559b7 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -923,9 +923,53 @@ if (!is_ios) {
   }
 
   # https://www.chromium.org/developers/testing/webkit-layout-tests
-  group("webkit_layout_tests") {
+
+  # TODO(dpranke): Get rid of this target once webkit_layout_tests_exparchive
+  # works reliably.
+  group("locally_swarmed_webkit_layout_tests") {
     testonly = true
 
+    deps = [
+      ":webkit_layout_tests_exparchive",
+    ]
+
+    data = [
+      # In addition to the test script, these files are needed for the
+      # test script to be able to call MB, GN, and the swarming and isolate
+      # binaries.
+      "//build/gn_helpers.py",
+      "//buildtools/",
+      "//testing/scripts/common.py",
+      "//testing/scripts/run_locally_swarmed_webkit_layout_tests.py",
+      "//tools/mb/",
+      "//tools/luci-go/",
+      "//tools/swarming_client/",
+    ]
+  }
+
+  # The _exparchive at the end of the name indicates to the isolate recipe
+  # that the isolate should be archived separately using the `exparchive`
+  # command, rather than as part of the normal `batcharchive` command.
+  group("webkit_layout_tests_exparchive") {
+    testonly = true
+    deps = [
+      ":some_webkit_layout_tests",
+    ]
+    data_deps = [
+      ":some_webkit_layout_tests",
+    ]
+
+    data = [
+      "//third_party/WebKit/LayoutTests/",
+    ]
+  }
+
+  # This target contains only a small subset of the layout tests,
+  # and is useful for testing with the regular isolate mechanism.
+  # To run the full layout test suite you need to use
+  # :webkit_layout_tests_exparchive, above, instead.
+  group("some_webkit_layout_tests") {
+    testonly = true
     data_deps = [
       "//content/shell:content_shell",
       "//tools/imagediff",
@@ -962,11 +1006,24 @@ if (!is_ios) {
     data = [
       "//testing/scripts/common.py",
       "//testing/xvfb.py",
-      "//testing/scripts/run_telemetry_as_googletest.py",
-      "//third_party/WebKit/LayoutTests/",
+      "//testing/scripts/run_isolated_script_test.py",
+      "//third_party/WebKit/LayoutTests/NeverFixTests",
+      "//third_party/WebKit/LayoutTests/SlowTests",
+      "//third_party/WebKit/LayoutTests/SmokeTests",
+      "//third_party/WebKit/LayoutTests/StaleTestExpectations",
+      "//third_party/WebKit/LayoutTests/TestExpectations",
+      "//third_party/WebKit/LayoutTests/VirtualTestSuites",
+      "//third_party/WebKit/LayoutTests/fast/html/",
       "//third_party/WebKit/Tools/Scripts/",
       "$root_build_dir/resources/inspector/",
     ]
+
+    if (is_android) {
+      data += [
+        "//third_party/catapult/",
+        "//build/android/",
+      ]
+    }
   }
 }