Add content_browsertests for testing cache control flags

content/shell/browser/shell.cc

Index: content/shell/browser/shell.cc
diff --git a/content/shell/browser/shell.cc b/content/shell/browser/shell.cc
index 1c1fb4b3d3a3bfbe4b4f302363db761dab214b02..c082cdb73505c0e9c84a3ae288ab801040f69e2b 100644
--- a/content/shell/browser/shell.cc
+++ b/content/shell/browser/shell.cc
@@ -264,6 +264,11 @@ void Shell::Reload() {
   web_contents_->Focus();
 }
 
+void Shell::ReloadBypassingCache() {
+  web_contents_->GetController().ReloadBypassingCache(false);
+  web_contents_->Focus();
+}
+
 void Shell::Stop() {
   web_contents_->Stop();
   web_contents_->Focus();