[fuchsia] Create DartComponentController for CFv2. (#28613)

Bug: fxb/79871

The code is still using the CFv1 implementation, so this should not affect the existing behavior.

For this version of the PR, I forked the existing DartComponentController. There were a few reasons for this:

Reduces the chance of the change breaking existing tests during Fuchsia GI.
Makes the V2 version of the DartComponentController simpler to read.
Makes it easier to switch over to using the V2 version of the DartComponentController once the migration is ready to happen (less cleanup).
The rate of changes to the DartComponentController is slow so there shouldn't be much maintenance required for the fork.
Changes to the DartRunner itself will happen in a follow-up PR - this PR only verifies that the ComponentController builds.

Relands GN and C++ changes for #27226 after rollback in #28036.

Author: akbiggs

ci/licenses_golden/licenses_flutter

@@ -1370,6 +1370,8 @@ FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/builtin_libraries.cc
 FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/builtin_libraries.h
 FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/dart_component_controller.cc
 FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/dart_component_controller.h
+FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/dart_component_controller_v2.cc
+FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/dart_component_controller_v2.h
 FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/dart_runner.cc
 FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/dart_runner.h
 FILE: ../../../flutter/shell/platform/fuchsia/dart_runner/embedder/builtin.dart

shell/platform/fuchsia/dart-pkg/fuchsia/sdk_ext/fuchsia.cc

@@ -117,10 +117,13 @@ void Initialize(fidl::InterfaceHandle<fuchsia::sys::Environment> environment,
   dart_state->class_library().add_provider("fuchsia",
                                            std::move(fuchsia_class_provider));
 
-  result = Dart_SetField(
-      library, ToDart("_environment"),
-      ToDart(zircon::dart::Handle::Create(environment.TakeChannel())));
-  FML_CHECK(!tonic::LogIfError(result));
+  // V2 components do not use the environment.
+  if (environment) {
+    result = Dart_SetField(
+        library, ToDart("_environment"),
+        ToDart(zircon::dart::Handle::Create(environment.TakeChannel())));
+    FML_CHECK(!tonic::LogIfError(result));
+  }
 
   if (directory_request) {
     result = Dart_SetField(

shell/platform/fuchsia/dart-pkg/fuchsia/sdk_ext/fuchsia.h

@@ -10,6 +10,7 @@
 namespace fuchsia {
 namespace dart {
 
+/// Initializes Dart bindings for the Fuchsia application model.
 void Initialize(fidl::InterfaceHandle<fuchsia::sys::Environment> environment,
                 zx::channel directory_request,
                 std::optional<zx::eventpair> view_ref);

shell/platform/fuchsia/dart_runner/BUILD.gn

@@ -38,6 +38,8 @@ template("runner") {
       "builtin_libraries.h",
       "dart_component_controller.cc",
       "dart_component_controller.h",
+      "dart_component_controller_v2.cc",
+      "dart_component_controller_v2.h",
       "dart_runner.cc",
       "dart_runner.h",
       "logging.h",
@@ -69,6 +71,7 @@ template("runner") {
              "//flutter/fml",
              "//flutter/shell/platform/fuchsia/dart-pkg/fuchsia",
              "//flutter/shell/platform/fuchsia/dart-pkg/zircon",
+             "$fuchsia_sdk_root/fidl:fuchsia.component.runner",
              "$fuchsia_sdk_root/pkg:async",
              "$fuchsia_sdk_root/pkg:async-cpp",
              "$fuchsia_sdk_root/pkg:async-default",
@@ -160,6 +163,7 @@ template("aot_runner_package") {
     binary = "dart_aot${product_suffix}_runner"
 
     cmx_file = rebase_path("meta/dart_aot${product_suffix}_runner.cmx")
+    cml_file = rebase_path("meta/dart_aot${product_suffix}_runner.cml")
 
     libraries = _common_runner_libs
 
@@ -220,6 +224,7 @@ template("jit_runner_package") {
     binary = "dart_jit${product_suffix}_runner"
 
     cmx_file = rebase_path("meta/dart_jit${product_suffix}_runner.cmx")
+    cml_file = rebase_path("meta/dart_jit${product_suffix}_runner.cml")
 
     libraries = _common_runner_libs