Convert some GN test support targets to static libs.

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index bab905c772f44b5837eea8be41009c5ce43b8472..5bf5c7f549bec790999d58ee01685b8fd50ef17f 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -50,7 +50,6 @@ static_library("test_support") {
     ":browsertest_base",
     ":content_test_mojo_bindings",
     "//base/third_party/dynamic_annotations",
-    "//cc",
     "//cc:test_support",
     "//cc/blink",
     "//cc/ipc",
@@ -207,7 +206,7 @@ static_library("test_support") {
 
 # browsertest_support can be used by targets that run content_shell based
 # browser tests.
-source_set("browsertest_support") {
+static_library("browsertest_support") {
   testonly = true
 
   # See comment at the top of //content/BUILD.gn for why this is disabled in
@@ -258,7 +257,7 @@ source_set("browsertest_support") {
 }
 
 # browsertest_base can be used by any browser test target.
-source_set("browsertest_base") {
+static_library("browsertest_base") {
   testonly = true
 
   sources = [