Extensions: Split the constants from the extensions_common target into its own...

Extensions: Split the constants from the extensions_common target into its own extensions_common_constants target.

The extensions constants are used in too many places and very hard to
get rid of. Making it into its own target so it can be included in all
builds, even when extensions are not enabled.

BUG=424746

Review URL: https://codereview.chromium.org/652623003

Cr-Commit-Position: refs/heads/master@{#300335}

extensions/common/BUILD.gn

@@ -11,6 +11,20 @@ mojom("mojo") {
   ]
 }
 
+# GYP version: extensions/extensions.gyp:extensions_common_constants
+source_set("common_constants") {
+  sources = [
+    "constants.cc",
+    "constants.h",
+  ]
+
+  if (is_win) {
+    cflags = [
+      "/wd4267", # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+    ]
+  }
+}
+
 # GYP version: extensions/extensions.gyp:extensions_common
 source_set("common") {
   sources = [
@@ -29,8 +43,6 @@ source_set("common") {
     "api/sockets/sockets_manifest_permission.h",
     "common_manifest_handlers.cc",
     "common_manifest_handlers.h",
-    "constants.cc",
-    "constants.h",
     "csp_validator.cc",
     "csp_validator.h",
     "dom_action_types.h",
@@ -201,6 +213,7 @@ source_set("common") {
   ]
 
   deps = [
+    ":common_constants",
     ":mojo",
     # TODO(benwells): figure out what to do with the api target and
     # api resources compiled into the chrome resource bundle.

extensions/extensions.gyp

@@ -21,6 +21,22 @@
         'common/stash.mojom',
       ],
     },
+    {
+      # GN version: //extensions/common
+      'target_name': 'extensions_common_constants',
+      'type': 'static_library',
+      'include_dirs': [
+        '..',
+        '<(INTERMEDIATE_DIR)',
+      ],
+      'sources': [
+        # Note: sources list duplicated in GN build.
+        'common/constants.cc',
+        'common/constants.h',
+      ],
+      # Disable c4267 warnings until we fix size_t to int truncations.
+      'msvs_disabled_warnings': [ 4267, ],
+    },
     {
       # GN version: //extensions/common
       'target_name': 'extensions_common',
@@ -40,6 +56,7 @@
         '../third_party/libxml/libxml.gyp:libxml',
         'extensions_resources.gyp:extensions_resources',
         'extensions_strings.gyp:extensions_strings',
+        'extensions_common_constants',
         'extensions_common_mojo',
       ],
       'include_dirs': [
@@ -63,8 +80,6 @@
         'common/api/sockets/sockets_manifest_permission.h',
         'common/common_manifest_handlers.cc',
         'common/common_manifest_handlers.h',
-        'common/constants.cc',
-        'common/constants.h',
         'common/csp_validator.cc',
         'common/csp_validator.h',
         'common/dom_action_types.h',