Expand is_linux to is_linux || is_chromeos.

Currnetly ,is_linux GN variable is set to true on Chrome OS build,
but it is planned to be set false. This CL is the preparation
to keep the bahavior compatible.

Bug: chromium:1110266
Test: Build locally.
Change-Id: Iffbfafe3ac5b00899804afa7471a04709046610a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/28340
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Hidehiko Abe <hidehiko@chromium.org>

scripts/dawn_component.gni

@@ -63,7 +63,7 @@ template("dawn_component") {
         "@executable_path/",
       ]
     }
-    if (is_linux && dawn_has_build) {
+    if ((is_linux || is_chromeos) && dawn_has_build) {
       configs = [ "//build/config/gcc:rpath_for_built_shared_libraries" ]
     }
   }

scripts/dawn_features.gni

@@ -52,8 +52,8 @@ declare_args() {
   dawn_enable_opengl = is_linux && !is_chromeos
 
   # Enables the compilation of Dawn's Vulkan backend
-  dawn_enable_vulkan =
-      is_linux || is_win || is_fuchsia || is_android || dawn_use_swiftshader
+  dawn_enable_vulkan = is_linux || is_chromeos || is_win || is_fuchsia ||
+                       is_android || dawn_use_swiftshader
 
   # Enable use of reflection compiler in spirv-cross. This is needed
   # if performing reflection on systems that the platform language

src/common/BUILD.gn

@@ -146,7 +146,7 @@ config("dawn_internal") {
 # This GN file is discovered by all Chromium builds, but common doesn't support
 # all of Chromium's OSes so we explicitly make the target visible only on
 # systems we know Dawn is able to compile on.
-if (is_win || is_linux || is_mac || is_fuchsia || is_android) {
+if (is_win || is_linux || is_chromeos || is_mac || is_fuchsia || is_android) {
   static_library("common") {
     sources = [
       "Assert.cpp",