Allow specifying both Dart and non-Dart fixtures in engine unit-tests. (flutter#9113)

* Allow specifying both Dart and non-Dart fixtures in engine unittests.

This fixes numerous issues in the way in which fixtures were managed
in the engine unit-tests.

* Instead of only being able to specify Dart fixtures, unit-tests may specify
  non-Dart fixtures as well. These are simply copied over to the fixtures
  directory known to the unit-test at runtime.
* An issue where numerous Dart files could be given to the kernel snapshotter
  has been addressed. It was anticipated that such a (legal) invocation to the
  kernel snapshotter would produce a snapshot with the contents of all the Dart
  files added to the root library. This is incorrect and the behavior in this
  case is undefined.
* Dart files referenced by the main Dart file are correctly tracked via a
  depfile.
* The snapshotter arguments have been cleaned up to get rid of unused
  arguments (`—strong`) and  the use of the VM product mode argument has been
  corrected to no longer depend on the Flutter product mode.

Author: chinmaygarde

flow/BUILD.gn

@@ -6,6 +6,8 @@ if (is_fuchsia) {
   import("//build/fuchsia/sdk.gni")
 }
 
+import("$flutter_root/testing/testing.gni")
+
 source_set("flow") {
   sources = [
     "compositor_context.cc",
@@ -100,6 +102,10 @@ source_set("flow") {
   }
 }
 
+test_fixtures("flow_fixtures") {
+  fixtures = []
+}
+
 executable("flow_unittests") {
   testonly = true
 
@@ -114,6 +120,7 @@ executable("flow_unittests") {
 
   deps = [
     ":flow",
+    ":flow_fixtures",
     "$flutter_root/fml",
     "//third_party/dart/runtime:libdart_jit",  # for tracing
     "//third_party/googletest:gtest",

fml/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/fuchsia/sdk.gni")
+import("$flutter_root/testing/testing.gni")
 
 source_set("fml") {
   sources = [
@@ -182,6 +183,10 @@ source_set("fml") {
   }
 }
 
+test_fixtures("fml_fixtures") {
+  fixtures = []
+}
+
 executable("fml_unittests") {
   testonly = true
 
@@ -208,6 +213,7 @@ executable("fml_unittests") {
   ]
 
   deps = [
+    ":fml_fixtures",
     "$flutter_root/fml",
     "$flutter_root/testing",
     "//third_party/dart/runtime:libdart_jit",

runtime/BUILD.gn

@@ -96,7 +96,7 @@ source_set("runtime") {
 }
 
 test_fixtures("runtime_fixtures") {
-  fixtures = [ "fixtures/runtime_test.dart" ]
+  dart_main = "fixtures/runtime_test.dart"
 }
 
 source_set("runtime_unittests_common") {

shell/common/BUILD.gn

@@ -147,7 +147,7 @@ shell_gpu_configuration("shell_unittests_gpu_configuration") {
 }
 
 test_fixtures("shell_unittests_fixtures") {
-  fixtures = [ "fixtures/shell_test.dart" ]
+  dart_main = "fixtures/shell_test.dart"
 }
 
 shell_host_executable("shell_unittests") {

shell/platform/common/cpp/client_wrapper/BUILD.gn

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("$flutter_root/testing/testing.gni")
 import("publish.gni")
 
 _wrapper_includes = [
@@ -75,6 +76,10 @@ source_set("client_wrapper_library_stubs") {
   ]
 }
 
+test_fixtures("client_wrapper_fixtures") {
+  fixtures = []
+}
+
 executable("client_wrapper_unittests") {
   testonly = true
 
@@ -91,6 +96,7 @@ executable("client_wrapper_unittests") {
 
   deps = [
     ":client_wrapper",
+    ":client_wrapper_fixtures",
     ":client_wrapper_library_stubs",
     "$flutter_root/testing",
 

shell/platform/darwin/BUILD.gn

@@ -4,6 +4,7 @@
 
 assert(is_mac || is_ios)
 
+import("$flutter_root/testing/testing.gni")
 import("framework_shared.gni")
 
 group("darwin") {
@@ -61,6 +62,10 @@ source_set("framework_shared") {
   public_configs = [ "$flutter_root:config" ]
 }
 
+test_fixtures("flutter_channels_fixtures") {
+  fixtures = []
+}
+
 executable("flutter_channels_unittests") {
   testonly = true
 
@@ -71,6 +76,7 @@ executable("flutter_channels_unittests") {
 
   deps = [
     ":flutter_channels",
+    ":flutter_channels_fixtures",
     "$flutter_root/testing",
     "//third_party/dart/runtime:libdart_jit",
   ]

shell/platform/embedder/BUILD.gn

@@ -57,7 +57,7 @@ source_set("embedder") {
 }
 
 test_fixtures("fixtures") {
-  fixtures = [ "fixtures/main.dart" ]
+  dart_main = "fixtures/main.dart"
 }
 
 executable("embedder_unittests") {

shell/platform/glfw/client_wrapper/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("$flutter_root/shell/platform/common/cpp/client_wrapper/publish.gni")
+import("$flutter_root/testing/testing.gni")
 
 _wrapper_includes = [
   "include/flutter/flutter_window.h",
@@ -63,6 +64,10 @@ source_set("client_wrapper_library_stubs_glfw") {
   ]
 }
 
+test_fixtures("client_wrapper_glfw_fixtures") {
+  fixtures = []
+}
+
 executable("client_wrapper_glfw_unittests") {
   testonly = true
 
@@ -73,6 +78,7 @@ executable("client_wrapper_glfw_unittests") {
 
   deps = [
     ":client_wrapper_glfw",
+    ":client_wrapper_glfw_fixtures",
     ":client_wrapper_library_stubs_glfw",
     "$flutter_root/shell/platform/common/cpp/client_wrapper:client_wrapper_library_stubs",
     "$flutter_root/testing",