WebUI: Provide a way to opt-out of --chrome_pass in js_type_check()

The --chrome_pass Closure compiler flag is only needed for code that relies on
cr.js (cr.define(), cr.exportPath() and friends). For JS code that has migrated
to JS modules --chrome_pass is not necessary.

Explicitly removing --chrome_pass not only makes type-checking faster, but
also ensures that eventually we don't depend on this pass at all.

Note that using |is_polymer3| also opts out a js_type_check() target from
--chrome_pass, but without the new |uses_js_modules| there is no easy way
for non-Polymer code to opt-out.

Note: With this change any JS code that uses JS modules must specify either
|uses_js_modules| or |is_polymer3| attributes.

Bug: 1028829
Change-Id: I4e019770e36ac460402123c5413be6c95e32fef2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1938248Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720597}

chrome/browser/resources/local_state/BUILD.gn

@@ -5,6 +5,7 @@
 import("//third_party/closure_compiler/compile_js.gni")
 
 js_type_check("closure_compile") {
+  uses_js_modules = true
   deps = [
     ":local_state",
   ]

chrome/browser/resources/media_router/BUILD.gn

@@ -5,6 +5,7 @@
 import("//third_party/closure_compiler/compile_js.gni")
 
 js_type_check("closure_compile") {
+  uses_js_modules = true
   deps = [
     ":media_router_internals",
   ]

chrome/browser/resources/offline_pages/BUILD.gn

@@ -5,6 +5,7 @@
 import("//third_party/closure_compiler/compile_js.gni")
 
 js_type_check("closure_compile") {
+  uses_js_modules = true
   deps = [
     ":offline_internals",
     ":offline_internals_browser_proxy",

chrome/browser/resources/reset_password/BUILD.gn

@@ -5,6 +5,7 @@
 import("//third_party/closure_compiler/compile_js.gni")
 
 js_type_check("closure_compile") {
+  uses_js_modules = true
   deps = [
     ":reset_password",
   ]

chrome/browser/resources/tab_strip/BUILD.gn

@@ -6,6 +6,7 @@ import("//third_party/closure_compiler/compile_js.gni")
 import("//tools/polymer/polymer.gni")
 
 js_type_check("closure_compile") {
+  uses_js_modules = true
   deps = [
     ":alert_indicator",
     ":alert_indicators",

chrome/browser/resources/webapks/BUILD.gn

@@ -5,6 +5,7 @@
 import("//third_party/closure_compiler/compile_js.gni")
 
 js_type_check("closure_compile") {
+  uses_js_modules = true
   deps = [
     ":about_webapks",
   ]

third_party/closure_compiler/closure_args.gni

@@ -39,7 +39,9 @@ default_closure_args = strict_error_checking_closure_args + [
                          "polymer_pass",
 
                          "jscomp_off=duplicate",
+                       ]
 
+js_modules_args = [
   "js_module_root=../../ui/webui/resources/",
   "js_module_root=gen/ui/webui/resources/",
 
@@ -47,22 +49,23 @@ default_closure_args = strict_error_checking_closure_args + [
   # gen/ui/webui/resources are js_module_roots.
   "module_resolution=BROWSER_WITH_TRANSFORMED_PREFIXES",
   "browser_resolver_prefix_replacements=\"chrome://resources/=./\"",
+
+  # Turn off primarily because cr.define() should not be used in any JS Modules
+  # based code, and secondarily because of b/133333578.
+  "chrome_pass=false",
 ]
 
-polymer3_args = [
+polymer3_args = js_modules_args + [
                   "browser_resolver_prefix_replacements=\"../polymer/polymer_bundled.min.js=../polymer/polymer_bundled.js\"",
                   "browser_resolver_prefix_replacements=\"chrome://resources/polymer/v3_0/polymer/polymer_bundled.min.js=../../third_party/polymer/v3_0/components-chromium/polymer/polymer_bundled.js\"",
                   "browser_resolver_prefix_replacements=\"chrome://resources/polymer/v3_0/=../../third_party/polymer/v3_0/components-chromium/\"",
 
-  # Turn off, primarily because cr.define() should not be used in any
-  # Polymer3/JS module code, but also because of b/133333578.
-  "chrome_pass=false",
                   "hide_warnings_for=externs.zip",
                   "hide_warnings_for=../../third_party/polymer/v3_0/components-chromium/",
                   "polymer_pass=false",
 
                   # Note: "2" is counter-intuitively the correct value to use for Polymer 3.
                   "polymer_version=2",
-]
+                ]
 
 default_disabled_closure_args = [ "jscomp_off=duplicate" ]

third_party/closure_compiler/compile_js.gni

@@ -161,10 +161,11 @@ template("js_binary") {
                              "deps",
                              "externs_list",
                              "extra_deps",
-                             "outputs",
                              "is_polymer3",
+                             "outputs",
                              "sources",
                              "testonly",
+                             "uses_js_modules",
                            ])
     args = [
       "--compiler",
@@ -224,6 +225,8 @@ template("js_binary") {
     }
     if (is_polymer3) {
       closure_flags += polymer3_args
+    } else if (defined(uses_js_modules) && uses_js_modules) {
+      closure_flags += js_modules_args
     }
 
     args += [ "--flags" ] + closure_flags
@@ -270,6 +273,7 @@ template("js_type_check") {
                                "deps",
                                "is_polymer3",
                                "testonly",
+                               "uses_js_modules",
                              ])
     }
   } else {

ui/webui/resources/cr_elements/BUILD.gn

@@ -189,6 +189,7 @@ group("polymer3_elements") {
 }
 
 js_type_check("cr_elements_module_resources") {
+  uses_js_modules = true
   deps = [
     ":cr_container_shadow_behavior.m",
   ]

ui/webui/resources/js/cr/BUILD.gn

@@ -13,6 +13,7 @@ js_type_check("closure_compile") {
 }
 
 js_type_check("closure_compile_modules") {
+  uses_js_modules = true
   deps = [
     ":event_target.m",
   ]