[Fuchsia] Conditionally include emulators and host tools in target.

Determine which host tools should be added to the isolates through new gn arg test_host_cpu
Determine whether emulator related files are needed through new gn arg test_isolate_uses_emulator

Bug: 1080854
Change-Id: I5d283a858717162160211f6084a7b4ca167e1215
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463846Reviewed-by: David Dorwin <ddorwin@chromium.org>
Commit-Queue: Chong Gu <chonggu@google.com>
Auto-Submit: Chong Gu <chonggu@google.com>
Cr-Commit-Position: refs/heads/master@{#817239}

DEPS

@@ -38,6 +38,7 @@ gclient_gn_args = [
   'checkout_android',
   'checkout_android_prebuilts_build_tools',
   'checkout_android_native_support',
+  'checkout_fuchsia_for_arm64_host',
   'checkout_google_benchmark',
   'checkout_ios_webkit',
   'checkout_nacl',

build/config/fuchsia/config.gni

@@ -4,10 +4,8 @@
 
 assert(is_fuchsia)
 
-# Compute the emulator paths.
+# Compute the AEMU path.
 aemu_root = "//third_party/aemu-${host_os}-${host_cpu}"
-qemu_root = "//third_party/qemu-${host_os}-${host_cpu}"
-qemu_arm64_root = "//third_party/qemu-${host_os}-arm64"
 
 # Compute the path to the arch-specific boot image directory.
 boot_image_root = "//third_party/fuchsia-sdk/images/${target_cpu}"

build/config/fuchsia/generate_runner_scripts.gni

@@ -17,12 +17,13 @@ declare_args() {
   # will be used.
   default_fuchsia_build_dir_for_installation = ""
 
-  # Architecture of the host tools included in Fuchsia test targets.
-  # Defaults to target_cpu.
-  fuchsia_override_host_tool_arch_for_isolated_testing = target_cpu
+  # CPU architecture of the host used to run the tests.
+  test_host_cpu = host_cpu
 
-  # A list that contains additional Fuchsia boot images to include in the test
-  # targets.
+  # Sets whether emulators need to be included in the test isolates
+  test_isolate_uses_emulator = true
+
+  # A list of additional Fuchsia boot images to include in the test isolates.
   fuchsia_additional_boot_images = []
 }
 
@@ -101,31 +102,40 @@ template("fuchsia_package_runner") {
       "//third_party/fuchsia-sdk/sdk/bin/fpave.sh",
       "//third_party/fuchsia-sdk/sdk/bin/fuchsia-common.sh",
       "//third_party/fuchsia-sdk/sdk/meta/manifest.json",
-      "${boot_image_root}/qemu/qemu-kernel.kernel",
-      "${boot_image_root}/qemu/storage-full.blk",
-      "${boot_image_root}/qemu/zircon-a.zbi",
     ]
 
-    if (host_cpu == "x64" && (host_os == "linux" || host_os == "mac")) {
-      data += [ "${aemu_root}/" ]
+    # TODO(crbug.com/1137662): Remove checkout_fuchsia_for_arm64_host from
+    # gclient_gn_args in //DEPS as well as this condition when builders have
+    # test_host_cpu set correctly.
+    if (checkout_fuchsia_for_arm64_host) {
+      test_host_cpu = "arm64"
+    }
+
+    if (test_host_cpu == "x64") {
+      data += [ "//third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer" ]
     }
 
     data += [
-      "//third_party/fuchsia-sdk/sdk/tools/${fuchsia_override_host_tool_arch_for_isolated_testing}/device-finder",
-      "//third_party/fuchsia-sdk/sdk/tools/${fuchsia_override_host_tool_arch_for_isolated_testing}/fvm",
-      "//third_party/fuchsia-sdk/sdk/tools/${fuchsia_override_host_tool_arch_for_isolated_testing}/merkleroot",
-      "//third_party/fuchsia-sdk/sdk/tools/${fuchsia_override_host_tool_arch_for_isolated_testing}/pm",
-      "//third_party/fuchsia-sdk/sdk/tools/${fuchsia_override_host_tool_arch_for_isolated_testing}/symbolize",
-      "//third_party/fuchsia-sdk/sdk/tools/${fuchsia_override_host_tool_arch_for_isolated_testing}/zbi",
+      "//third_party/fuchsia-sdk/sdk/tools/${test_host_cpu}/device-finder",
+      "//third_party/fuchsia-sdk/sdk/tools/${test_host_cpu}/fvm",
+      "//third_party/fuchsia-sdk/sdk/tools/${test_host_cpu}/merkleroot",
+      "//third_party/fuchsia-sdk/sdk/tools/${test_host_cpu}/pm",
+      "//third_party/fuchsia-sdk/sdk/tools/${test_host_cpu}/symbolize",
+      "//third_party/fuchsia-sdk/sdk/tools/${test_host_cpu}/zbi",
     ]
 
-    if (target_cpu == "arm64") {
-      data += [ "${qemu_arm64_root}/" ]
-    } else {
+    if (test_isolate_uses_emulator) {
       data += [
-        "${qemu_root}/",
-        "//third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer",
+        "${boot_image_root}/qemu/qemu-kernel.kernel",
+        "${boot_image_root}/qemu/storage-full.blk",
+        "${boot_image_root}/qemu/zircon-a.zbi",
+        "//third_party/qemu-${host_os}-${test_host_cpu}/",
       ]
+
+      # Include AEMU for x64 emulator hosts.
+      if (test_host_cpu == "x64") {
+        data += [ "${aemu_root}/" ]
+      }
     }
 
     foreach(fuchsia_additional_boot_image, fuchsia_additional_boot_images) {