[Blimp] Refactor Blimp test engine with embedded test server and URL rewriting

blimp/engine/app/blimp_content_browser_client.cc

Index: blimp/engine/app/blimp_content_browser_client.cc
diff --git a/blimp/engine/app/blimp_content_browser_client.cc b/blimp/engine/app/blimp_content_browser_client.cc
index 5e8c42b361bbb22727e74bcba9f63c360ab08984..e3958f6c1e066c229c327e880ed1e92baffa432d 100644
--- a/blimp/engine/app/blimp_content_browser_client.cc
+++ b/blimp/engine/app/blimp_content_browser_client.cc
@@ -27,6 +27,11 @@ content::BrowserMainParts* BlimpContentBrowserClient::CreateBrowserMainParts(
   return blimp_browser_main_parts_;
 }
 
+void BlimpContentBrowserClient::SetBrowserMainPartsForTesting(
+    BlimpBrowserMainParts* blimp_browser_main_parts) {
+  blimp_browser_main_parts_ = blimp_browser_main_parts;
+}
+
 void BlimpContentBrowserClient::OverrideWebkitPrefs(
     content::RenderViewHost* render_view_host,
     content::WebPreferences* prefs) {