Use ANGLE gni file for .gn exec script whitelist.

This means we will no longer need to maintain the exec script
whitelist in two places for ANGLE (in Chrome and ANGLE itself).

Tbr: dpranke@chromium.org
Bug: angleproject:2339
Change-Id: I4ad9d2d4a66cbfeb2245785c07839489a7e4ad58
Reviewed-on: https://chromium-review.googlesource.com/902197Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534770}

.gn

@@ -3,6 +3,7 @@
 # file, run "gn help dotfile" at the command line.
 
 import("//build/dotfile_settings.gni")
+import("//third_party/angle/dotfile_settings.gni")
 
 # The location of the build configuration file.
 buildconfig = "//build/config/BUILDCONFIG.gn"
@@ -231,7 +232,9 @@ check_targets = [
 #      files and passes them to a script, it will always be correct.
 
 exec_script_whitelist =
-    build_dotfile_settings.exec_script_whitelist + [
+    build_dotfile_settings.exec_script_whitelist +
+    angle_dotfile_settings.exec_script_whitelist +
+    [
       # Whitelist entries for //build should go into
       # //build/dotfile_settings.gni instead, so that they can be shared
       # with other repos. The entries in this list should be only for files
@@ -248,9 +251,6 @@ exec_script_whitelist =
       "//remoting/host/installer/win/generate_clsids.gni",
 
       # TODO(dpranke): Get these from the appropriate repos instead.
-      "//third_party/angle/BUILD.gn",
-      "//third_party/angle/src/tests/BUILD.gn",
-      "//third_party/angle/src/vulkan_support/BUILD.gn",
       "//third_party/catapult/tracing/BUILD.gn",
       "//third_party/google_input_tools/inputview.gni",