Fix //content/test:test_support under component builds.

content/ppapi_plugin/BUILD.gn

Index: content/ppapi_plugin/BUILD.gn
diff --git a/content/ppapi_plugin/BUILD.gn b/content/ppapi_plugin/BUILD.gn
index 971a060492eb8b5cc102b6af64dd8a12b529ecaf..b4a6704e125f857a58b6833be428b859c90ac2e5 100644
--- a/content/ppapi_plugin/BUILD.gn
+++ b/content/ppapi_plugin/BUILD.gn
@@ -2,7 +2,21 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("ppapi_plugin") {
+group("ppapi_plugin") {
+  visibility = [ "//content/*" ]
+
+  if (is_component_build) {
+    public_deps = [
+      "//content",
+    ]
+  } else {
+    public_deps = [
+      ":ppapi_plugin_sources",
+    ]
+  }
+}
+
+source_set("ppapi_plugin_sources") {
   visibility = [ "//content/*" ]
 
   sources = [