Make gn generate on Win

BUG=
R=brettw

Review URL: https://codereview.chromium.org/576743002

Cr-Commit-Position: refs/heads/master@{#295283}

build/toolchain/win/BUILD.gn

@@ -26,6 +26,10 @@ concurrent_links = exec_script("../get_concurrent_links.py", [], "value")
 #  environment: File name of environment file.
 #  force_win64 (optional): value for this build arg.
 template("msvc_toolchain") {
+  if (defined(invoker.concurrent_links)) {
+    concurrent_links = invoker.concurrent_links
+  }
+
   env = invoker.environment
 
   toolchain(target_name) {

content/BUILD.gn

@@ -39,7 +39,6 @@ config("content_implementation") {
 
 content_shared_components = [
   "//content/gpu",
-  "//content/plugin",
   "//content/public/browser:browser_sources",
   "//content/public/child:child_sources",
   "//content/public/common:common_sources",