[Android] Generate scripts at build time to run android tests.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 30b05fb43308dc5a555fc0c41c7d7698d44e0235..7baa7d312f5b7e38621fefd99cca5a28b1a80fa4 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -1278,6 +1278,7 @@ if (!is_android) {
       # TODO: remove --gc-sections for Debug builds (crbug.com/159847).
       ldflags = [ "-Wl,--gc-sections" ]
       deps += [ "//testing/android/native_test:native_test_native_code" ]
+      isolate_file = "../unit_tests.isolate"
     } else {
       sources +=
           rebase_path(unit_gypi_values.chrome_unit_tests_non_android_sources,