Use use_webview_provider gn arg instead of gn_isolate_map.pyl args

This is a follow up to http://crrev.com/c/1926920 which adds a
use_webview_provider arg to instrumentation_test_apk. Unfortunately, the
use of --use-webview-provider in gn_isolate_map.pyl for
webview_cts_tests could not be converted to the gn arg because they do
some tricky things and don't use instrumentation_test_apk.

Change-Id: I7843d1210072f989b60bf08561786ac939eee2a2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930100Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718318}

android_webview/tools/automated_ui_tests/BUILD.gn

@@ -69,5 +69,5 @@ instrumentation_test_apk("webview_ui_test_app_test_apk") {
   data = [
     "test/data/",
   ]
-  additional_apks = [ system_webview_apk_target ]
+  use_webview_provider = system_webview_apk_target
 }

android_webview/tools/system_webview_shell/BUILD.gn

@@ -95,5 +95,5 @@ instrumentation_test_apk("system_webview_shell_layout_test_apk") {
     "//third_party/blink/web_tests/webexposed/global-interface-listing.html",
     "//third_party/blink/web_tests/webexposed/global-interface-listing-expected.txt",
   ]
-  additional_apks = [ system_webview_apk_target ]
+  use_webview_provider = system_webview_apk_target
 }

testing/buildbot/gn_isolate_map.pyl

@@ -2645,8 +2645,6 @@
   },
   "system_webview_shell_layout_test_apk": {
     "args": [
-      "--use-webview-provider",
-      "apks/SystemWebView.apk",
       "--replace-system-package",
       "org.chromium.webview_shell,apks/SystemWebViewShell.apk",
       "--use-apk-under-test-flags-file",
@@ -3085,8 +3083,6 @@
   },
   "webview_ui_test_app_test_apk": {
     "args": [
-      "--use-webview-provider",
-      "apks/SystemWebView.apk",
       "--use-apk-under-test-flags-file",
     ],
     "label": "//android_webview/tools/automated_ui_tests:webview_ui_test_app_test_apk",