[NoStatePrefetch] Support only GET and HEAD

chrome/browser/prerender/prerender_contents.cc

Index: chrome/browser/prerender/prerender_contents.cc
diff --git a/chrome/browser/prerender/prerender_contents.cc b/chrome/browser/prerender/prerender_contents.cc
index 5e4b3adde081cf5946bff597331e285539392fad..c4570c07ea7d0ee47fa10a4eba5258cc23c0cbd5 100644
--- a/chrome/browser/prerender/prerender_contents.cc
+++ b/chrome/browser/prerender/prerender_contents.cc
@@ -58,6 +58,16 @@ namespace prerender {
 
 namespace {
 
+// Valid HTTP methods for both prefetch and prerendering.
+const char* const kValidHttpMethods[] = {
+    "GET", "HEAD",
+};
+
+// Additional valid HTTP methods for prerendering.
+const char* const kValidHttpMethodsForPrerendering[] = {
+    "OPTIONS", "POST", "TRACE",
+};
+
 void ResumeThrottles(
     std::vector<base::WeakPtr<PrerenderResourceThrottle> > throttles) {
   for (size_t i = 0; i < throttles.size(); i++) {
@@ -223,6 +233,27 @@ void PrerenderContents::SetPrerenderMode(PrerenderMode mode) {
   prerender_mode_ = mode;
 }
 
+bool PrerenderContents::IsValidHttpMethod(const std::string& method) {
+  DCHECK_NE(prerender_mode(), NO_PRERENDER);
+  // method has been canonicalized to upper case at this point so we can just
+  // compare them.
+  DCHECK_EQ(method, base::ToUpperASCII(method));
+  for (size_t i = 0; i < arraysize(kValidHttpMethods); ++i) {

[mmenke, 2016/09/20 15:25:32]

optional nit:  for both the loops, can just do:  for (const auto& :
kValidHttpMethods)

[droger, 2016/09/21 09:57:48]

Done.

+    if (method.compare(kValidHttpMethods[i]) == 0)

[mmenke, 2016/09/20 15:25:32]

Know this is what the old code did, but maybe we should just be using == instead
of compare?  It's potentially faster, since compare has to care about the
difference of < vs >, while == does not.  Same for the loop below.

[droger, 2016/09/21 09:57:48]

TIL

According to this:
http://stackoverflow.com/questions/9158894/differences-between-c-string-and-c...

== is implemented using compare() in our case, so the performance should be the
same.
However == is really what we want conceptually.

Also note that if both strings are std::strings, == can be faster since it
compares first the size of the strings before iterating them.
This does not apply to us here, because we're comparing a C-string to a
std::string.

Done.

+      return true;
+  }
+
+  if (prerender_mode() == PREFETCH_ONLY)
+    return false;
+
+  for (size_t i = 0; i < arraysize(kValidHttpMethodsForPrerendering); ++i) {
+    if (method.compare(kValidHttpMethodsForPrerendering[i]) == 0)
+      return true;
+  }
+
+  return false;
+}
+
 // static
 PrerenderContents::Factory* PrerenderContents::CreateFactory() {
   return new PrerenderContentsFactoryImpl();