Add more components tests to GN build.

components/web_cache/browser/BUILD.gn

Index: components/web_cache/browser/BUILD.gn
diff --git a/components/web_cache/browser/BUILD.gn b/components/web_cache/browser/BUILD.gn
index e1d24d64399107638170899f2f214053d9e2983d..e64a2d5ca4aed9bd06c36848a3898dbe61f07033 100644
--- a/components/web_cache/browser/BUILD.gn
+++ b/components/web_cache/browser/BUILD.gn
@@ -2,8 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-static_library("browser") {
-  output_name = "web_cache_browser"
+source_set("browser") {
   sources = [
     "web_cache_manager.cc",
     "web_cache_manager.h",
@@ -19,3 +18,16 @@ static_library("browser") {
     "//third_party/WebKit/public:blink",
   ]
 }
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "web_cache_manager_unittest.cc",
+  ]
+  deps = [
+    ":browser",
+    "//base",
+    "//content/test:test_support",
+    "//testing/gtest",
+  ]
+}